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 $33.41   5.477%   $35.2399   $35.24   $35.25   $35.20  
  Purchase #2 $198.58   7.497%   $213.4675   $213.47   $213.45   $213.50  
  Purchase #3 $29.50   6.113%   $31.3033   $31.30   $31.30   $31.30  
  Purchase #4 $230.68   5.555%   $243.4943   $243.49   $243.50   $243.50  
  Purchase #5 $220.93   9.644%   $242.2365   $242.24   $242.25   $242.20  
  Purchase #6 $105.61   10.659%   $116.867   $116.87   $116.85   $116.90  
  Purchase #7 $24.64   5.137%   $25.9058   $25.91   $25.90   $25.90  
  7 purchase totals = $843.35       $908.5143   $908.52   $908.50   $908.50