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 $87.31   10.562%   $96.5317   $96.53   $96.55   $96.50  
  Purchase #2 $109.59   8.843%   $119.281   $119.28   $119.30   $119.30  
  Purchase #3 $233.64   5.420%   $246.3033   $246.30   $246.30   $246.30  
  Purchase #4 $36.51   5.277%   $38.4366   $38.44   $38.45   $38.40  
  Purchase #5 $164.49   5.107%   $172.8905   $172.89   $172.90   $172.90  
  Purchase #6 $192.43   13.632%   $218.6621   $218.66   $218.65   $218.70  
  Purchase #7 $68.44   9.494%   $74.9377   $74.94   $74.95   $74.90  
  7 purchase totals = $892.41       $967.0429   $967.04   $967.10   $967.00