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 $88.94   6.572%   $94.7851   $94.79   $94.80   $94.80  
  Purchase #2 $197.91   7.465%   $212.684   $212.68   $212.70   $212.70  
  Purchase #3 $92.31   11.478%   $102.9053   $102.91   $102.90   $102.90  
  Purchase #4 $249.77   10.503%   $276.0033   $276.00   $276.00   $276.00  
  Purchase #5 $162.85   5.371%   $171.5967   $171.60   $171.60   $171.60  
  Purchase #6 $212.84   6.339%   $226.3319   $226.33   $226.35   $226.30  
  Purchase #7 $170.89   4.560%   $178.6826   $178.68   $178.70   $178.70  
  7 purchase totals = $1,175.51       $1,262.9889   $1,262.99   $1,263.05   $1,263.00