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 $118.77   5.252%   $125.0078   $125.01   $125.00   $125.00  
  Purchase #2 $160.97   10.258%   $177.4823   $177.48   $177.50   $177.50  
  Purchase #3 $183.51   11.779%   $205.1256   $205.13   $205.15   $205.10  
  Purchase #4 $36.85   7.865%   $39.7483   $39.75   $39.75   $39.70  
  Purchase #5 $188.85   7.476%   $202.9684   $202.97   $202.95   $203.00  
  Purchase #6 $201.78   4.201%   $210.2568   $210.26   $210.25   $210.30  
  Purchase #7 $59.94   13.384%   $67.9624   $67.96   $67.95   $68.00  
  7 purchase totals = $950.67       $1,028.5516   $1,028.56   $1,028.55   $1,028.60