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 $173.72   5.255%   $182.849   $182.85   $182.85   $182.80  
  Purchase #2 $112.52   11.223%   $125.1481   $125.15   $125.15   $125.10  
  Purchase #3 $33.57   9.547%   $36.7749   $36.77   $36.75   $36.80  
  Purchase #4 $192.77   5.722%   $203.8003   $203.80   $203.80   $203.80  
  Purchase #5 $123.91   5.401%   $130.6024   $130.60   $130.60   $130.60  
  Purchase #6 $24.59   7.801%   $26.5083   $26.51   $26.50   $26.50  
  Purchase #7 $60.51   4.155%   $63.0242   $63.02   $63.00   $63.00  
  7 purchase totals = $721.59       $768.7072   $768.70   $768.65   $768.60