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 $88.36   7.750%   $95.2079   $95.21   $95.20   $95.20  
  Purchase #2 $204.30   5.543%   $215.6243   $215.62   $215.60   $215.60  
  Purchase #3 $235.89   3.276%   $243.6178   $243.62   $243.60   $243.60  
  Purchase #4 $83.93   9.664%   $92.041   $92.04   $92.05   $92.00  
  Purchase #5 $123.98   6.385%   $131.8961   $131.90   $131.90   $131.90  
  Purchase #6 $221.48   12.868%   $249.98   $249.98   $250.00   $250.00  
  Purchase #7 $194.55   12.596%   $219.0555   $219.06   $219.05   $219.10  
  7 purchase totals = $1,152.49       $1,247.4226   $1,247.43   $1,247.40   $1,247.40