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 $191.48   5.753%   $202.4958   $202.50   $202.50   $202.50  
  Purchase #2 $96.96   8.254%   $104.9631   $104.96   $104.95   $105.00  
  Purchase #3 $28.38   13.812%   $32.2998   $32.30   $32.30   $32.30  
  Purchase #4 $243.35   10.508%   $268.9212   $268.92   $268.90   $268.90  
  Purchase #5 $203.87   10.348%   $224.9665   $224.97   $224.95   $225.00  
  Purchase #6 $138.53   9.207%   $151.2845   $151.28   $151.30   $151.30  
  Purchase #7 $22.67   4.326%   $23.6507   $23.65   $23.65   $23.70  
  7 purchase totals = $925.24       $1,008.5816   $1,008.58   $1,008.55   $1,008.70