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 $61.82   5.550%   $65.251   $65.25   $65.25   $65.30  
  Purchase #2 $140.35   10.725%   $155.4025   $155.40   $155.40   $155.40  
  Purchase #3 $119.96   4.594%   $125.471   $125.47   $125.45   $125.50  
  Purchase #4 $202.43   8.191%   $219.011   $219.01   $219.00   $219.00  
  Purchase #5 $121.42   6.650%   $129.4944   $129.49   $129.50   $129.50  
  Purchase #6 $204.97   6.384%   $218.0553   $218.06   $218.05   $218.10  
  Purchase #7 $166.26   13.635%   $188.9296   $188.93   $188.95   $188.90  
  7 purchase totals = $1,017.21       $1,101.6148   $1,101.61   $1,101.60   $1,101.70