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 $69.33   6.748%   $74.0084   $74.01   $74.00   $74.00  
  Purchase #2 $39.52   4.615%   $41.3438   $41.34   $41.35   $41.30  
  Purchase #3 $72.36   6.523%   $77.08   $77.08   $77.10   $77.10  
  Purchase #4 $188.88   8.335%   $204.6231   $204.62   $204.60   $204.60  
  Purchase #5 $226.82   4.692%   $237.4624   $237.46   $237.45   $237.50  
  Purchase #6 $154.53   4.125%   $160.9044   $160.90   $160.90   $160.90  
  Purchase #7 $217.85   10.660%   $241.0728   $241.07   $241.05   $241.10  
  7 purchase totals = $969.29       $1,036.4949   $1,036.48   $1,036.45   $1,036.50