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 $87.99   7.446%   $94.5417   $94.54   $94.55   $94.50  
  Purchase #2 $228.84   3.859%   $237.6709   $237.67   $237.65   $237.70  
  Purchase #3 $107.35   8.298%   $116.2579   $116.26   $116.25   $116.30  
  Purchase #4 $204.85   6.244%   $217.6408   $217.64   $217.65   $217.60  
  Purchase #5 $124.64   6.859%   $133.1891   $133.19   $133.20   $133.20  
  Purchase #6 $164.29   10.457%   $181.4698   $181.47   $181.45   $181.50  
  Purchase #7 $240.57   6.208%   $255.5046   $255.50   $255.50   $255.50  
  7 purchase totals = $1,158.53       $1,236.2748   $1,236.27   $1,236.25   $1,236.30