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 $203.59   11.143%   $226.276   $226.28   $226.30   $226.30  
  Purchase #2 $219.90   10.685%   $243.3963   $243.40   $243.40   $243.40  
  Purchase #3 $217.76   6.163%   $231.1805   $231.18   $231.20   $231.20  
  Purchase #4 $239.30   5.168%   $251.667   $251.67   $251.65   $251.70  
  Purchase #5 $44.29   5.271%   $46.6245   $46.62   $46.60   $46.60  
  Purchase #6 $97.39   4.606%   $101.8758   $101.88   $101.90   $101.90  
  Purchase #7 $159.50   5.489%   $168.255   $168.26   $168.25   $168.30  
  7 purchase totals = $1,181.73       $1,269.2751   $1,269.29   $1,269.30   $1,269.40