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 $204.31   10.504%   $225.7707   $225.77   $225.75   $225.80  
  Purchase #2 $195.26   3.159%   $201.4283   $201.43   $201.45   $201.40  
  Purchase #3 $205.56   11.279%   $228.7451   $228.75   $228.75   $228.70  
  Purchase #4 $91.36   11.153%   $101.5494   $101.55   $101.55   $101.50  
  Purchase #5 $146.80   12.851%   $165.6653   $165.67   $165.65   $165.70  
  Purchase #6 $57.75   4.743%   $60.4891   $60.49   $60.50   $60.50  
  Purchase #7 $125.95   8.354%   $136.4719   $136.47   $136.45   $136.50  
  7 purchase totals = $1,026.99       $1,120.1198   $1,120.13   $1,120.10   $1,120.10