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 $184.34   11.717%   $205.9391   $205.94   $205.95   $205.90  
  Purchase #2 $55.43   11.340%   $61.7158   $61.72   $61.70   $61.70  
  Purchase #3 $194.28   8.846%   $211.466   $211.47   $211.45   $211.50  
  Purchase #4 $222.87   10.611%   $246.5187   $246.52   $246.50   $246.50  
  Purchase #5 $245.76   3.179%   $253.5727   $253.57   $253.55   $253.60  
  Purchase #6 $91.82   11.593%   $102.4647   $102.46   $102.45   $102.50  
  Purchase #7 $22.82   10.627%   $25.2451   $25.25   $25.25   $25.20  
  7 purchase totals = $1,017.32       $1,106.9221   $1,106.93   $1,106.85   $1,106.90