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 $57.94   5.313%   $61.0184   $61.02   $61.00   $61.00  
  Purchase #2 $72.72   6.805%   $77.6686   $77.67   $77.65   $77.70  
  Purchase #3 $208.33   8.787%   $226.636   $226.64   $226.65   $226.60  
  Purchase #4 $173.29   5.381%   $182.6147   $182.61   $182.60   $182.60  
  Purchase #5 $104.78   5.341%   $110.3763   $110.38   $110.40   $110.40  
  Purchase #6 $82.67   8.695%   $89.8582   $89.86   $89.85   $89.90  
  Purchase #7 $6.94   3.847%   $7.207   $7.21   $7.20   $7.20  
  7 purchase totals = $706.67       $755.3792   $755.39   $755.35   $755.40