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 $192.84   5.253%   $202.9699   $202.97   $202.95   $203.00  
  Purchase #2 $218.52   7.526%   $234.9658   $234.97   $234.95   $235.00  
  Purchase #3 $199.26   7.393%   $213.9913   $213.99   $214.00   $214.00  
  Purchase #4 $67.93   9.403%   $74.3175   $74.32   $74.30   $74.30  
  Purchase #5 $163.60   3.681%   $169.6221   $169.62   $169.60   $169.60  
  Purchase #6 $48.78   4.756%   $51.1   $51.10   $51.10   $51.10  
  Purchase #7 $91.95   7.403%   $98.7571   $98.76   $98.75   $98.80  
  7 purchase totals = $982.88       $1,045.7237   $1,045.73   $1,045.65   $1,045.80