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 $63.50   13.340%   $71.9709   $71.97   $71.95   $72.00  
  Purchase #2 $204.62   6.852%   $218.6406   $218.64   $218.65   $218.60  
  Purchase #3 $222.31   4.495%   $232.3028   $232.30   $232.30   $232.30  
  Purchase #4 $22.69   8.513%   $24.6216   $24.62   $24.60   $24.60  
  Purchase #5 $234.93   10.485%   $259.5624   $259.56   $259.55   $259.60  
  Purchase #6 $207.79   9.818%   $228.1908   $228.19   $228.20   $228.20  
  Purchase #7 $132.91   5.380%   $140.0606   $140.06   $140.05   $140.10  
  7 purchase totals = $1,088.75       $1,175.3497   $1,175.34   $1,175.30   $1,175.40