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 $216.25   11.312%   $240.7122   $240.71   $240.70   $240.70  
  Purchase #2 $56.67   6.352%   $60.2697   $60.27   $60.25   $60.30  
  Purchase #3 $205.34   13.692%   $233.4552   $233.46   $233.45   $233.50  
  Purchase #4 $202.42   3.431%   $209.365   $209.37   $209.35   $209.40  
  Purchase #5 $213.46   10.530%   $235.9373   $235.94   $235.95   $235.90  
  Purchase #6 $10.47   8.769%   $11.3881   $11.39   $11.40   $11.40  
  Purchase #7 $206.79   3.347%   $213.7113   $213.71   $213.70   $213.70  
  7 purchase totals = $1,111.40       $1,204.8388   $1,204.85   $1,204.80   $1,204.90