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 $212.90   6.620%   $226.994   $226.99   $227.00   $227.00  
  Purchase #2 $215.64   9.292%   $235.6773   $235.68   $235.70   $235.70  
  Purchase #3 $38.50   7.162%   $41.2574   $41.26   $41.25   $41.30  
  Purchase #4 $157.35   3.709%   $163.1861   $163.19   $163.20   $163.20  
  Purchase #5 $234.57   9.399%   $256.6172   $256.62   $256.60   $256.60  
  Purchase #6 $187.34   6.607%   $199.7176   $199.72   $199.70   $199.70  
  Purchase #7 $165.38   3.459%   $171.1005   $171.10   $171.10   $171.10  
  7 purchase totals = $1,211.68       $1,294.5501   $1,294.56   $1,294.55   $1,294.60