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 $91.98   3.529%   $95.226   $95.23   $95.25   $95.20  
  Purchase #2 $216.89   5.608%   $229.0532   $229.05   $229.05   $229.10  
  Purchase #3 $238.77   11.356%   $265.8847   $265.88   $265.90   $265.90  
  Purchase #4 $230.94   8.392%   $250.3205   $250.32   $250.30   $250.30  
  Purchase #5 $107.49   12.249%   $120.6565   $120.66   $120.65   $120.70  
  Purchase #6 $83.93   3.467%   $86.8399   $86.84   $86.85   $86.80  
  Purchase #7 $159.95   5.783%   $169.1999   $169.20   $169.20   $169.20  
  7 purchase totals = $1,129.95       $1,217.1807   $1,217.18   $1,217.20   $1,217.20