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 $63.36   8.755%   $68.9072   $68.91   $68.90   $68.90  
  Purchase #2 $222.34   7.832%   $239.7537   $239.75   $239.75   $239.80  
  Purchase #3 $204.53   10.279%   $225.5536   $225.55   $225.55   $225.60  
  Purchase #4 $121.43   3.502%   $125.6825   $125.68   $125.70   $125.70  
  Purchase #5 $125.47   5.620%   $132.5214   $132.52   $132.50   $132.50  
  Purchase #6 $205.33   11.765%   $229.4871   $229.49   $229.50   $229.50  
  Purchase #7 $65.90   11.504%   $73.4811   $73.48   $73.50   $73.50  
  7 purchase totals = $1,008.36       $1,095.3866   $1,095.38   $1,095.40   $1,095.50