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 $50.79   3.465%   $52.5499   $52.55   $52.55   $52.50  
  Purchase #2 $245.27   7.506%   $263.68   $263.68   $263.70   $263.70  
  Purchase #3 $68.33   5.296%   $71.9488   $71.95   $71.95   $71.90  
  Purchase #4 $170.55   7.747%   $183.7625   $183.76   $183.75   $183.80  
  Purchase #5 $62.47   5.757%   $66.0664   $66.07   $66.05   $66.10  
  Purchase #6 $103.35   3.374%   $106.837   $106.84   $106.85   $106.80  
  Purchase #7 $102.52   13.679%   $116.5437   $116.54   $116.55   $116.50  
  7 purchase totals = $803.28       $861.3883   $861.39   $861.40   $861.30