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 $68.27   4.359%   $71.2459   $71.25   $71.25   $71.20  
  Purchase #2 $202.98   11.528%   $226.3795   $226.38   $226.40   $226.40  
  Purchase #3 $219.95   10.113%   $242.1935   $242.19   $242.20   $242.20  
  Purchase #4 $104.33   6.163%   $110.7599   $110.76   $110.75   $110.80  
  Purchase #5 $132.52   6.686%   $141.3803   $141.38   $141.40   $141.40  
  Purchase #6 $240.55   11.423%   $268.028   $268.03   $268.05   $268.00  
  Purchase #7 $215.85   9.232%   $235.7773   $235.78   $235.80   $235.80  
  7 purchase totals = $1,184.45       $1,295.7644   $1,295.77   $1,295.85   $1,295.80