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 $41.38   7.614%   $44.5307   $44.53   $44.55   $44.50  
  Purchase #2 $167.40   5.413%   $176.4614   $176.46   $176.45   $176.50  
  Purchase #3 $104.64   9.648%   $114.7357   $114.74   $114.75   $114.70  
  Purchase #4 $178.39   9.801%   $195.874   $195.87   $195.85   $195.90  
  Purchase #5 $181.57   3.519%   $187.9594   $187.96   $187.95   $188.00  
  Purchase #6 $50.80   12.784%   $57.2943   $57.29   $57.30   $57.30  
  Purchase #7 $211.53   10.398%   $233.5249   $233.52   $233.50   $233.50  
  7 purchase totals = $935.71       $1,010.3804   $1,010.37   $1,010.35   $1,010.40