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 $55.29   11.593%   $61.6998   $61.70   $61.70   $61.70  
  Purchase #2 $183.78   5.301%   $193.5222   $193.52   $193.50   $193.50  
  Purchase #3 $70.37   5.761%   $74.424   $74.42   $74.40   $74.40  
  Purchase #4 $212.31   10.723%   $235.076   $235.08   $235.10   $235.10  
  Purchase #5 $233.75   9.223%   $255.3088   $255.31   $255.30   $255.30  
  Purchase #6 $87.56   13.695%   $99.5513   $99.55   $99.55   $99.60  
  Purchase #7 $39.72   11.709%   $44.3708   $44.37   $44.35   $44.40  
  7 purchase totals = $882.78       $963.9529   $963.95   $963.90   $964.00