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 $55.26   12.205%   $62.0045   $62.00   $62.00   $62.00  
  Purchase #2 $61.55   8.320%   $66.671   $66.67   $66.65   $66.70  
  Purchase #3 $162.34   5.560%   $171.3661   $171.37   $171.35   $171.40  
  Purchase #4 $76.70   7.648%   $82.566   $82.57   $82.55   $82.60  
  Purchase #5 $206.53   3.453%   $213.6615   $213.66   $213.65   $213.70  
  Purchase #6 $189.94   11.579%   $211.9332   $211.93   $211.95   $211.90  
  Purchase #7 $128.86   11.671%   $143.8993   $143.90   $143.90   $143.90  
  7 purchase totals = $881.18       $952.1016   $952.10   $952.05   $952.20