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 $153.33   9.400%   $167.743   $167.74   $167.75   $167.70  
  Purchase #2 $55.65   4.174%   $57.9728   $57.97   $57.95   $58.00  
  Purchase #3 $191.25   7.581%   $205.7487   $205.75   $205.75   $205.70  
  Purchase #4 $161.88   6.421%   $172.2743   $172.27   $172.25   $172.30  
  Purchase #5 $147.48   10.874%   $163.517   $163.52   $163.50   $163.50  
  Purchase #6 $61.72   8.502%   $66.9674   $66.97   $66.95   $67.00  
  Purchase #7 $220.31   6.507%   $234.6456   $234.65   $234.65   $234.60  
  7 purchase totals = $991.62       $1,068.8688   $1,068.87   $1,068.80   $1,068.80