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 $67.76   9.657%   $74.3036   $74.30   $74.30   $74.30  
  Purchase #2 $198.83   6.860%   $212.4697   $212.47   $212.45   $212.50  
  Purchase #3 $110.38   4.541%   $115.3924   $115.39   $115.40   $115.40  
  Purchase #4 $246.40   4.148%   $256.6207   $256.62   $256.60   $256.60  
  Purchase #5 $147.62   12.170%   $165.5854   $165.59   $165.60   $165.60  
  Purchase #6 $193.79   10.323%   $213.7949   $213.79   $213.80   $213.80  
  Purchase #7 $165.83   6.241%   $176.1795   $176.18   $176.20   $176.20  
  7 purchase totals = $1,130.61       $1,214.3462   $1,214.34   $1,214.35   $1,214.40