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 $28.67   13.532%   $32.5496   $32.55   $32.55   $32.50  
  Purchase #2 $205.29   13.805%   $233.6303   $233.63   $233.65   $233.60  
  Purchase #3 $99.97   6.641%   $106.609   $106.61   $106.60   $106.60  
  Purchase #4 $241.54   11.700%   $269.8002   $269.80   $269.80   $269.80  
  Purchase #5 $182.67   8.718%   $198.5952   $198.60   $198.60   $198.60  
  Purchase #6 $146.41   3.844%   $152.038   $152.04   $152.05   $152.00  
  Purchase #7 $164.65   6.350%   $175.1053   $175.11   $175.10   $175.10  
  7 purchase totals = $1,069.20       $1,168.3276   $1,168.34   $1,168.35   $1,168.20