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 $162.79   4.123%   $169.5018   $169.50   $169.50   $169.50  
  Purchase #2 $95.37   11.528%   $106.3643   $106.36   $106.35   $106.40  
  Purchase #3 $67.56   12.541%   $76.0327   $76.03   $76.05   $76.00  
  Purchase #4 $234.72   8.345%   $254.3074   $254.31   $254.30   $254.30  
  Purchase #5 $58.65   4.566%   $61.328   $61.33   $61.35   $61.30  
  Purchase #6 $144.98   3.372%   $149.8687   $149.87   $149.85   $149.90  
  Purchase #7 $237.29   5.314%   $249.8996   $249.90   $249.90   $249.90  
  7 purchase totals = $1,001.36       $1,067.3025   $1,067.30   $1,067.30   $1,067.30