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 $48.83   7.786%   $52.6319   $52.63   $52.65   $52.60  
  Purchase #2 $207.48   5.206%   $218.2814   $218.28   $218.30   $218.30  
  Purchase #3 $234.85   5.510%   $247.7902   $247.79   $247.80   $247.80  
  Purchase #4 $170.48   13.472%   $193.4471   $193.45   $193.45   $193.40  
  Purchase #5 $119.82   5.439%   $126.337   $126.34   $126.35   $126.30  
  Purchase #6 $167.45   9.830%   $183.9103   $183.91   $183.90   $183.90  
  Purchase #7 $57.52   5.207%   $60.5151   $60.52   $60.50   $60.50  
  7 purchase totals = $1,006.43       $1,082.9130   $1,082.92   $1,082.95   $1,082.80