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 $93.66   3.694%   $97.1198   $97.12   $97.10   $97.10  
  Purchase #2 $194.54   9.823%   $213.6497   $213.65   $213.65   $213.60  
  Purchase #3 $120.74   12.373%   $135.6792   $135.68   $135.70   $135.70  
  Purchase #4 $102.82   9.175%   $112.2537   $112.25   $112.25   $112.30  
  Purchase #5 $76.84   5.188%   $80.8265   $80.83   $80.85   $80.80  
  Purchase #6 $56.65   5.640%   $59.8451   $59.85   $59.85   $59.80  
  Purchase #7 $56.55   11.526%   $63.068   $63.07   $63.05   $63.10  
  7 purchase totals = $701.80       $762.4420   $762.45   $762.45   $762.40