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 $211.76   10.278%   $233.5247   $233.52   $233.50   $233.50  
  Purchase #2 $180.30   11.357%   $200.7767   $200.78   $200.80   $200.80  
  Purchase #3 $225.78   9.512%   $247.2562   $247.26   $247.25   $247.30  
  Purchase #4 $93.26   13.851%   $106.1774   $106.18   $106.20   $106.20  
  Purchase #5 $243.65   12.128%   $273.1999   $273.20   $273.20   $273.20  
  Purchase #6 $176.92   9.472%   $193.6779   $193.68   $193.70   $193.70  
  Purchase #7 $216.31   7.766%   $233.1086   $233.11   $233.10   $233.10  
  7 purchase totals = $1,347.98       $1,487.7214   $1,487.73   $1,487.75   $1,487.80