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 $44.58   4.151%   $46.4305   $46.43   $46.45   $46.40  
  Purchase #2 $199.95   5.169%   $210.2854   $210.29   $210.30   $210.30  
  Purchase #3 $116.72   9.585%   $127.9076   $127.91   $127.90   $127.90  
  Purchase #4 $39.94   11.545%   $44.5511   $44.55   $44.55   $44.60  
  Purchase #5 $237.80   8.829%   $258.7954   $258.80   $258.80   $258.80  
  Purchase #6 $113.30   8.251%   $122.6484   $122.65   $122.65   $122.60  
  Purchase #7 $209.51   11.152%   $232.8746   $232.87   $232.85   $232.90  
  7 purchase totals = $961.80       $1,043.4930   $1,043.50   $1,043.50   $1,043.50