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 $190.58   11.221%   $211.965   $211.97   $211.95   $212.00  
  Purchase #2 $113.97   11.551%   $127.1347   $127.13   $127.15   $127.10  
  Purchase #3 $47.47   11.669%   $53.0093   $53.01   $53.00   $53.00  
  Purchase #4 $241.44   6.829%   $257.9279   $257.93   $257.95   $257.90  
  Purchase #5 $173.59   4.853%   $182.0143   $182.01   $182.00   $182.00  
  Purchase #6 $151.89   12.114%   $170.29   $170.29   $170.30   $170.30  
  Purchase #7 $164.76   13.399%   $186.8362   $186.84   $186.85   $186.80  
  7 purchase totals = $1,083.70       $1,189.1774   $1,189.18   $1,189.20   $1,189.10