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 $34.35   8.160%   $37.153   $37.15   $37.15   $37.20  
  Purchase #2 $160.32   7.237%   $171.9224   $171.92   $171.90   $171.90  
  Purchase #3 $246.53   11.869%   $275.7906   $275.79   $275.80   $275.80  
  Purchase #4 $100.27   11.815%   $112.1169   $112.12   $112.10   $112.10  
  Purchase #5 $113.73   5.282%   $119.7372   $119.74   $119.75   $119.70  
  Purchase #6 $202.48   10.463%   $223.6655   $223.67   $223.65   $223.70  
  Purchase #7 $239.70   9.195%   $261.7404   $261.74   $261.75   $261.70  
  7 purchase totals = $1,097.38       $1,202.1260   $1,202.13   $1,202.10   $1,202.10