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 $56.33   6.524%   $60.005   $60.01   $60.00   $60.00  
  Purchase #2 $120.83   4.859%   $126.7011   $126.70   $126.70   $126.70  
  Purchase #3 $114.63   11.600%   $127.9271   $127.93   $127.95   $127.90  
  Purchase #4 $33.96   6.585%   $36.1963   $36.20   $36.20   $36.20  
  Purchase #5 $43.47   11.540%   $48.4864   $48.49   $48.50   $48.50  
  Purchase #6 $118.29   11.612%   $132.0258   $132.03   $132.05   $132.00  
  Purchase #7 $183.78   10.423%   $202.9354   $202.94   $202.95   $202.90  
  7 purchase totals = $671.29       $734.2771   $734.30   $734.35   $734.20