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 $182.51   6.598%   $194.552   $194.55   $194.55   $194.60  
  Purchase #2 $129.66   11.106%   $144.06   $144.06   $144.05   $144.10  
  Purchase #3 $108.92   9.537%   $119.3077   $119.31   $119.30   $119.30  
  Purchase #4 $158.79   5.634%   $167.7362   $167.74   $167.75   $167.70  
  Purchase #5 $190.96   11.533%   $212.9834   $212.98   $213.00   $213.00  
  Purchase #6 $137.94   6.562%   $146.9916   $146.99   $147.00   $147.00  
  Purchase #7 $33.83   11.206%   $37.621   $37.62   $37.60   $37.60  
  7 purchase totals = $942.61       $1,023.2519   $1,023.25   $1,023.25   $1,023.30