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 $84.39   5.406%   $88.9521   $88.95   $88.95   $89.00  
  Purchase #2 $116.86   7.248%   $125.33   $125.33   $125.35   $125.30  
  Purchase #3 $57.84   4.613%   $60.5082   $60.51   $60.50   $60.50  
  Purchase #4 $210.55   5.352%   $221.8186   $221.82   $221.80   $221.80  
  Purchase #5 $232.96   7.675%   $250.8397   $250.84   $250.85   $250.80  
  Purchase #6 $72.69   5.300%   $76.5426   $76.54   $76.55   $76.50  
  Purchase #7 $196.98   7.294%   $211.3477   $211.35   $211.35   $211.30  
  7 purchase totals = $972.27       $1,035.3389   $1,035.34   $1,035.35   $1,035.20