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 $33.68   6.140%   $35.748   $35.75   $35.75   $35.70  
  Purchase #2 $89.98   13.131%   $101.7953   $101.80   $101.80   $101.80  
  Purchase #3 $153.55   10.874%   $170.247   $170.25   $170.25   $170.20  
  Purchase #4 $246.84   12.148%   $276.8261   $276.83   $276.85   $276.80  
  Purchase #5 $5.38   4.564%   $5.6255   $5.63   $5.65   $5.60  
  Purchase #6 $51.86   5.126%   $54.5183   $54.52   $54.50   $54.50  
  Purchase #7 $45.28   11.821%   $50.6325   $50.63   $50.65   $50.60  
  7 purchase totals = $626.57       $695.3927   $695.41   $695.45   $695.20