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 $47.45   10.827%   $52.5874   $52.59   $52.60   $52.60  
  Purchase #2 $61.48   11.222%   $68.3793   $68.38   $68.40   $68.40  
  Purchase #3 $245.50   8.846%   $267.2169   $267.22   $267.20   $267.20  
  Purchase #4 $101.59   4.674%   $106.3383   $106.34   $106.35   $106.30  
  Purchase #5 $213.97   3.509%   $221.4782   $221.48   $221.50   $221.50  
  Purchase #6 $183.52   13.141%   $207.6364   $207.64   $207.65   $207.60  
  Purchase #7 $83.89   8.655%   $91.1507   $91.15   $91.15   $91.20  
  7 purchase totals = $937.40       $1,014.7872   $1,014.80   $1,014.85   $1,014.80