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 $62.42   7.306%   $66.9804   $66.98   $67.00   $67.00  
  Purchase #2 $218.61   5.207%   $229.993   $229.99   $230.00   $230.00  
  Purchase #3 $19.77   11.694%   $22.0819   $22.08   $22.10   $22.10  
  Purchase #4 $184.68   10.416%   $203.9163   $203.92   $203.90   $203.90  
  Purchase #5 $164.93   11.562%   $183.9992   $184.00   $184.00   $184.00  
  Purchase #6 $51.32   11.720%   $57.3347   $57.33   $57.35   $57.30  
  Purchase #7 $231.38   5.169%   $243.34   $243.34   $243.35   $243.30  
  7 purchase totals = $933.11       $1,007.6455   $1,007.64   $1,007.70   $1,007.60