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 $233.37   4.830%   $244.6418   $244.64   $244.65   $244.60  
  Purchase #2 $247.32   8.479%   $268.2903   $268.29   $268.30   $268.30  
  Purchase #3 $150.94   10.548%   $166.8612   $166.86   $166.85   $166.90  
  Purchase #4 $219.29   11.208%   $243.868   $243.87   $243.85   $243.90  
  Purchase #5 $173.53   10.644%   $192.0005   $192.00   $192.00   $192.00  
  Purchase #6 $249.88   5.317%   $263.1661   $263.17   $263.15   $263.20  
  Purchase #7 $46.83   12.573%   $52.7179   $52.72   $52.70   $52.70  
  7 purchase totals = $1,321.16       $1,431.5458   $1,431.55   $1,431.50   $1,431.60