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 $207.95   12.410%   $233.7566   $233.76   $233.75   $233.80  
  Purchase #2 $185.52   6.444%   $197.4749   $197.47   $197.45   $197.50  
  Purchase #3 $90.62   4.486%   $94.6852   $94.69   $94.70   $94.70  
  Purchase #4 $60.43   13.746%   $68.7367   $68.74   $68.75   $68.70  
  Purchase #5 $202.26   3.554%   $209.4483   $209.45   $209.45   $209.40  
  Purchase #6 $179.70   13.504%   $203.9667   $203.97   $203.95   $204.00  
  Purchase #7 $167.51   7.837%   $180.6378   $180.64   $180.65   $180.60  
  7 purchase totals = $1,093.99       $1,188.7062   $1,188.72   $1,188.70   $1,188.70