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 $84.79   12.745%   $95.5965   $95.60   $95.60   $95.60  
  Purchase #2 $49.55   3.657%   $51.362   $51.36   $51.35   $51.40  
  Purchase #3 $89.44   7.620%   $96.2553   $96.26   $96.25   $96.30  
  Purchase #4 $159.51   3.227%   $164.6574   $164.66   $164.65   $164.70  
  Purchase #5 $161.42   10.220%   $177.9171   $177.92   $177.90   $177.90  
  Purchase #6 $137.65   11.330%   $153.2457   $153.25   $153.25   $153.20  
  Purchase #7 $203.83   13.478%   $231.3022   $231.30   $231.30   $231.30  
  7 purchase totals = $886.19       $970.3362   $970.35   $970.30   $970.40