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 $69.52   3.540%   $71.981   $71.98   $72.00   $72.00  
  Purchase #2 $195.76   3.546%   $202.7016   $202.70   $202.70   $202.70  
  Purchase #3 $18.26   3.594%   $18.9163   $18.92   $18.90   $18.90  
  Purchase #4 $22.88   7.554%   $24.6084   $24.61   $24.60   $24.60  
  Purchase #5 $103.32   13.500%   $117.2682   $117.27   $117.25   $117.30  
  Purchase #6 $138.45   7.297%   $148.5527   $148.55   $148.55   $148.60  
  Purchase #7 $140.88   13.322%   $159.648   $159.65   $159.65   $159.60  
  7 purchase totals = $689.07       $743.6762   $743.68   $743.65   $743.70