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 $93.71   13.228%   $106.106   $106.11   $106.10   $106.10  
  Purchase #2 $52.57   4.611%   $54.994   $54.99   $55.00   $55.00  
  Purchase #3 $150.59   13.171%   $170.4242   $170.42   $170.40   $170.40  
  Purchase #4 $138.59   7.273%   $148.6697   $148.67   $148.65   $148.70  
  Purchase #5 $199.31   9.146%   $217.5389   $217.54   $217.55   $217.50  
  Purchase #6 $159.28   6.136%   $169.0534   $169.05   $169.05   $169.10  
  Purchase #7 $152.28   10.432%   $168.1658   $168.17   $168.15   $168.20  
  7 purchase totals = $946.33       $1,034.9520   $1,034.95   $1,034.90   $1,035.00