Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $110.34   6.703%   $117.7361   $117.74   $117.75   $117.70  
  Purchase #2 $178.94   8.393%   $193.9584   $193.96   $193.95   $194.00  
  Purchase #3 $242.97   13.771%   $276.4294   $276.43   $276.45   $276.40  
  Purchase #4 $183.85   5.436%   $193.8441   $193.84   $193.85   $193.80  
  Purchase #5 $228.71   9.841%   $251.2174   $251.22   $251.20   $251.20  
  Purchase #6 $223.48   11.164%   $248.4293   $248.43   $248.45   $248.40  
  Purchase #7 $163.84   13.589%   $186.1042   $186.10   $186.10   $186.10  
  7 purchase totals = $1,332.13       $1,467.7189   $1,467.72   $1,467.75   $1,467.60