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 $24.52   4.399%   $25.5986   $25.60   $25.60   $25.60  
  Purchase #2 $219.79   9.645%   $240.9887   $240.99   $241.00   $241.00  
  Purchase #3 $44.83   9.415%   $49.0507   $49.05   $49.05   $49.10  
  Purchase #4 $202.95   3.447%   $209.9457   $209.95   $209.95   $209.90  
  Purchase #5 $207.54   13.482%   $235.5205   $235.52   $235.50   $235.50  
  Purchase #6 $244.71   3.472%   $253.2063   $253.21   $253.20   $253.20  
  Purchase #7 $94.58   11.664%   $105.6118   $105.61   $105.60   $105.60  
  7 purchase totals = $1,038.92       $1,119.9223   $1,119.93   $1,119.90   $1,119.90