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 $88.62   10.323%   $97.7682   $97.77   $97.75   $97.80  
  Purchase #2 $121.92   9.494%   $133.4951   $133.50   $133.50   $133.50  
  Purchase #3 $231.41   13.570%   $262.8123   $262.81   $262.80   $262.80  
  Purchase #4 $220.36   10.412%   $243.3039   $243.30   $243.30   $243.30  
  Purchase #5 $22.48   11.727%   $25.1162   $25.12   $25.10   $25.10  
  Purchase #6 $136.49   11.225%   $151.811   $151.81   $151.80   $151.80  
  Purchase #7 $145.59   11.405%   $162.1945   $162.19   $162.20   $162.20  
  7 purchase totals = $966.87       $1,076.5012   $1,076.50   $1,076.45   $1,076.50