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 $85.52   8.199%   $92.5318   $92.53   $92.55   $92.50  
  Purchase #2 $120.41   7.639%   $129.6081   $129.61   $129.60   $129.60  
  Purchase #3 $118.34   11.724%   $132.2142   $132.21   $132.20   $132.20  
  Purchase #4 $117.77   4.417%   $122.9719   $122.97   $122.95   $123.00  
  Purchase #5 $183.79   5.873%   $194.584   $194.58   $194.60   $194.60  
  Purchase #6 $218.53   12.273%   $245.3502   $245.35   $245.35   $245.40  
  Purchase #7 $124.73   4.262%   $130.046   $130.05   $130.05   $130.00  
  7 purchase totals = $969.09       $1,047.3062   $1,047.30   $1,047.30   $1,047.30