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 $206.97   4.121%   $215.4992   $215.50   $215.50   $215.50  
  Purchase #2 $213.72   5.804%   $226.1243   $226.12   $226.10   $226.10  
  Purchase #3 $99.84   10.853%   $110.6756   $110.68   $110.70   $110.70  
  Purchase #4 $54.31   3.469%   $56.194   $56.19   $56.20   $56.20  
  Purchase #5 $242.84   5.796%   $256.915   $256.92   $256.90   $256.90  
  Purchase #6 $118.65   6.782%   $126.6968   $126.70   $126.70   $126.70  
  Purchase #7 $191.30   11.453%   $213.2096   $213.21   $213.20   $213.20  
  7 purchase totals = $1,127.63       $1,205.3145   $1,205.32   $1,205.30   $1,205.30