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 $213.95   10.776%   $237.0053   $237.01   $237.00   $237.00  
  Purchase #2 $75.39   4.185%   $78.5451   $78.55   $78.55   $78.50  
  Purchase #3 $160.85   6.708%   $171.6398   $171.64   $171.65   $171.60  
  Purchase #4 $212.29   13.336%   $240.601   $240.60   $240.60   $240.60  
  Purchase #5 $192.93   10.407%   $213.0082   $213.01   $213.00   $213.00  
  Purchase #6 $174.90   7.461%   $187.9493   $187.95   $187.95   $187.90  
  Purchase #7 $173.81   11.761%   $194.2518   $194.25   $194.25   $194.30  
  7 purchase totals = $1,204.12       $1,323.0005   $1,323.01   $1,323.00   $1,322.90