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 $44.28   5.551%   $46.738   $46.74   $46.75   $46.70  
  Purchase #2 $160.27   10.273%   $176.7345   $176.73   $176.75   $176.70  
  Purchase #3 $82.32   7.558%   $88.5417   $88.54   $88.55   $88.50  
  Purchase #4 $188.79   7.756%   $203.4326   $203.43   $203.45   $203.40  
  Purchase #5 $39.45   9.541%   $43.2139   $43.21   $43.20   $43.20  
  Purchase #6 $33.56   3.233%   $34.645   $34.65   $34.65   $34.60  
  Purchase #7 $91.31   4.494%   $95.4135   $95.41   $95.40   $95.40  
  7 purchase totals = $639.98       $688.7192   $688.71   $688.75   $688.50