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 $31.53   13.542%   $35.7998   $35.80   $35.80   $35.80  
  Purchase #2 $194.85   6.817%   $208.1329   $208.13   $208.15   $208.10  
  Purchase #3 $110.47   9.721%   $121.2088   $121.21   $121.20   $121.20  
  Purchase #4 $74.50   3.758%   $77.2997   $77.30   $77.30   $77.30  
  Purchase #5 $195.86   4.802%   $205.2652   $205.27   $205.25   $205.30  
  Purchase #6 $153.74   3.722%   $159.4622   $159.46   $159.45   $159.50  
  Purchase #7 $199.98   12.851%   $225.6794   $225.68   $225.70   $225.70  
  7 purchase totals = $960.93       $1,032.8480   $1,032.85   $1,032.85   $1,032.90