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 $38.61   12.745%   $43.5308   $43.53   $43.55   $43.50  
  Purchase #2 $165.96   7.536%   $178.4667   $178.47   $178.45   $178.50  
  Purchase #3 $212.53   13.363%   $240.9304   $240.93   $240.95   $240.90  
  Purchase #4 $193.60   11.332%   $215.5388   $215.54   $215.55   $215.50  
  Purchase #5 $249.73   5.607%   $263.7324   $263.73   $263.75   $263.70  
  Purchase #6 $219.64   7.687%   $236.5237   $236.52   $236.50   $236.50  
  Purchase #7 $243.26   4.803%   $254.9438   $254.94   $254.95   $254.90  
  7 purchase totals = $1,323.33       $1,433.6666   $1,433.66   $1,433.70   $1,433.50