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 $196.43   11.475%   $218.9703   $218.97   $218.95   $219.00  
  Purchase #2 $48.95   13.434%   $55.5259   $55.53   $55.55   $55.50  
  Purchase #3 $182.64   11.508%   $203.6582   $203.66   $203.65   $203.70  
  Purchase #4 $53.94   12.644%   $60.7602   $60.76   $60.75   $60.80  
  Purchase #5 $8.93   11.574%   $9.9636   $9.96   $9.95   $10.00  
  Purchase #6 $244.46   6.116%   $259.4112   $259.41   $259.40   $259.40  
  Purchase #7 $111.73   5.673%   $118.0684   $118.07   $118.05   $118.10  
  7 purchase totals = $847.08       $926.3578   $926.36   $926.30   $926.50