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 $101.44   9.188%   $110.7603   $110.76   $110.75   $110.80  
  Purchase #2 $218.29   3.352%   $225.6071   $225.61   $225.60   $225.60  
  Purchase #3 $160.29   8.373%   $173.7111   $173.71   $173.70   $173.70  
  Purchase #4 $69.43   8.248%   $75.1566   $75.16   $75.15   $75.20  
  Purchase #5 $69.62   4.310%   $72.6206   $72.62   $72.60   $72.60  
  Purchase #6 $243.56   3.339%   $251.6925   $251.69   $251.70   $251.70  
  Purchase #7 $136.78   10.133%   $150.6399   $150.64   $150.65   $150.60  
  7 purchase totals = $999.41       $1,060.1881   $1,060.19   $1,060.15   $1,060.20