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 $64.64   12.220%   $72.539   $72.54   $72.55   $72.50  
  Purchase #2 $174.92   11.102%   $194.3396   $194.34   $194.35   $194.30  
  Purchase #3 $47.75   9.203%   $52.1444   $52.14   $52.15   $52.10  
  Purchase #4 $226.84   10.694%   $251.0983   $251.10   $251.10   $251.10  
  Purchase #5 $53.28   5.411%   $56.163   $56.16   $56.15   $56.20  
  Purchase #6 $39.90   13.661%   $45.3507   $45.35   $45.35   $45.40  
  Purchase #7 $75.51   11.205%   $83.9709   $83.97   $83.95   $84.00  
  7 purchase totals = $682.84       $755.6059   $755.60   $755.60   $755.60