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 $92.86   5.562%   $98.0249   $98.02   $98.00   $98.00  
  Purchase #2 $235.79   13.805%   $268.3408   $268.34   $268.35   $268.30  
  Purchase #3 $246.46   4.867%   $258.4552   $258.46   $258.45   $258.50  
  Purchase #4 $122.31   13.475%   $138.7913   $138.79   $138.80   $138.80  
  Purchase #5 $111.43   13.554%   $126.5332   $126.53   $126.55   $126.50  
  Purchase #6 $153.34   12.537%   $172.5642   $172.56   $172.55   $172.60  
  Purchase #7 $232.94   7.650%   $250.7599   $250.76   $250.75   $250.80  
  7 purchase totals = $1,195.13       $1,313.4695   $1,313.46   $1,313.45   $1,313.50