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 $53.84   9.485%   $58.9467   $58.95   $58.95   $58.90  
  Purchase #2 $210.89   4.604%   $220.5994   $220.60   $220.60   $220.60  
  Purchase #3 $65.30   11.730%   $72.9597   $72.96   $72.95   $73.00  
  Purchase #4 $85.30   10.514%   $94.2684   $94.27   $94.25   $94.30  
  Purchase #5 $179.59   3.197%   $185.3315   $185.33   $185.35   $185.30  
  Purchase #6 $219.68   3.793%   $228.0125   $228.01   $228.00   $228.00  
  Purchase #7 $91.85   11.421%   $102.3402   $102.34   $102.35   $102.30  
  7 purchase totals = $906.45       $962.4584   $962.46   $962.45   $962.40