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 $162.93   6.317%   $173.2223   $173.22   $173.20   $173.20  
  Purchase #2 $185.35   5.387%   $195.3348   $195.33   $195.35   $195.30  
  Purchase #3 $110.48   7.426%   $118.6842   $118.68   $118.70   $118.70  
  Purchase #4 $179.72   13.761%   $204.4513   $204.45   $204.45   $204.50  
  Purchase #5 $69.98   3.441%   $72.388   $72.39   $72.40   $72.40  
  Purchase #6 $162.71   8.488%   $176.5208   $176.52   $176.50   $176.50  
  Purchase #7 $180.43   8.240%   $195.2974   $195.30   $195.30   $195.30  
  7 purchase totals = $1,051.60       $1,135.8988   $1,135.89   $1,135.90   $1,135.90