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 $69.66   5.672%   $73.6111   $73.61   $73.60   $73.60  
  Purchase #2 $218.56   8.735%   $237.6512   $237.65   $237.65   $237.70  
  Purchase #3 $31.96   3.642%   $33.124   $33.12   $33.10   $33.10  
  Purchase #4 $11.55   11.858%   $12.9196   $12.92   $12.90   $12.90  
  Purchase #5 $47.80   12.756%   $53.8974   $53.90   $53.90   $53.90  
  Purchase #6 $69.76   8.521%   $75.7042   $75.70   $75.70   $75.70  
  Purchase #7 $243.84   8.184%   $263.7959   $263.80   $263.80   $263.80  
  7 purchase totals = $693.13       $750.7034   $750.70   $750.65   $750.70