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 $208.51   11.780%   $233.0725   $233.07   $233.05   $233.10  
  Purchase #2 $104.59   13.436%   $118.6427   $118.64   $118.65   $118.60  
  Purchase #3 $208.93   3.276%   $215.7745   $215.77   $215.75   $215.80  
  Purchase #4 $56.75   10.741%   $62.8455   $62.85   $62.85   $62.80  
  Purchase #5 $41.26   6.722%   $44.0335   $44.03   $44.05   $44.00  
  Purchase #6 $175.65   8.793%   $191.0949   $191.09   $191.10   $191.10  
  Purchase #7 $112.37   7.246%   $120.5123   $120.51   $120.50   $120.50  
  7 purchase totals = $908.06       $985.9759   $985.96   $985.95   $985.90