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 $93.91   3.721%   $97.4044   $97.40   $97.40   $97.40  
  Purchase #2 $22.76   5.272%   $23.9599   $23.96   $23.95   $24.00  
  Purchase #3 $97.84   3.564%   $101.327   $101.33   $101.35   $101.30  
  Purchase #4 $120.29   11.501%   $134.1246   $134.12   $134.10   $134.10  
  Purchase #5 $5.66   10.396%   $6.2484   $6.25   $6.25   $6.20  
  Purchase #6 $168.94   3.658%   $175.1198   $175.12   $175.10   $175.10  
  Purchase #7 $142.90   10.338%   $157.673   $157.67   $157.65   $157.70  
  7 purchase totals = $652.30       $695.8571   $695.85   $695.80   $695.80