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 $182.58   6.414%   $194.2907   $194.29   $194.30   $194.30  
  Purchase #2 $170.85   4.281%   $178.1641   $178.16   $178.15   $178.20  
  Purchase #3 $19.44   12.359%   $21.8426   $21.84   $21.85   $21.80  
  Purchase #4 $68.58   9.408%   $75.032   $75.03   $75.05   $75.00  
  Purchase #5 $152.67   10.203%   $168.2469   $168.25   $168.25   $168.20  
  Purchase #6 $196.58   11.196%   $218.5891   $218.59   $218.60   $218.60  
  Purchase #7 $232.81   8.395%   $252.3544   $252.35   $252.35   $252.40  
  7 purchase totals = $1,023.51       $1,108.5198   $1,108.51   $1,108.55   $1,108.50