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 $184.95   4.658%   $193.565   $193.57   $193.55   $193.60  
  Purchase #2 $203.93   8.824%   $221.9248   $221.92   $221.90   $221.90  
  Purchase #3 $62.27   11.456%   $69.4037   $69.40   $69.40   $69.40  
  Purchase #4 $78.43   5.388%   $82.6558   $82.66   $82.65   $82.70  
  Purchase #5 $213.62   8.282%   $231.312   $231.31   $231.30   $231.30  
  Purchase #6 $178.71   7.430%   $191.9882   $191.99   $192.00   $192.00  
  Purchase #7 $234.35   4.372%   $244.5958   $244.60   $244.60   $244.60  
  7 purchase totals = $1,156.26       $1,235.4453   $1,235.45   $1,235.40   $1,235.50