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 $59.70   3.794%   $61.965   $61.97   $61.95   $62.00  
  Purchase #2 $27.46   6.617%   $29.277   $29.28   $29.30   $29.30  
  Purchase #3 $231.98   13.790%   $263.97   $263.97   $263.95   $264.00  
  Purchase #4 $108.42   11.279%   $120.6487   $120.65   $120.65   $120.60  
  Purchase #5 $91.74   9.267%   $100.2415   $100.24   $100.25   $100.20  
  Purchase #6 $162.81   8.406%   $176.4958   $176.50   $176.50   $176.50  
  Purchase #7 $246.26   9.429%   $269.4799   $269.48   $269.50   $269.50  
  7 purchase totals = $928.37       $1,022.0779   $1,022.09   $1,022.10   $1,022.10