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 $183.26   6.164%   $194.5561   $194.56   $194.55   $194.60  
  Purchase #2 $142.82   5.703%   $150.965   $150.97   $150.95   $151.00  
  Purchase #3 $177.71   10.396%   $196.1847   $196.18   $196.20   $196.20  
  Purchase #4 $47.32   13.666%   $53.7868   $53.79   $53.80   $53.80  
  Purchase #5 $198.75   13.802%   $226.1815   $226.18   $226.20   $226.20  
  Purchase #6 $87.61   6.142%   $92.991   $92.99   $93.00   $93.00  
  Purchase #7 $25.57   10.365%   $28.2203   $28.22   $28.20   $28.20  
  7 purchase totals = $863.04       $942.8854   $942.89   $942.90   $943.00