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 $83.98   13.432%   $95.2602   $95.26   $95.25   $95.30  
  Purchase #2 $198.52   10.187%   $218.7432   $218.74   $218.75   $218.70  
  Purchase #3 $202.29   5.548%   $213.513   $213.51   $213.50   $213.50  
  Purchase #4 $229.48   5.138%   $241.2707   $241.27   $241.25   $241.30  
  Purchase #5 $172.93   8.694%   $187.9645   $187.96   $187.95   $188.00  
  Purchase #6 $222.78   9.118%   $243.0931   $243.09   $243.10   $243.10  
  Purchase #7 $175.57   11.764%   $196.2241   $196.22   $196.20   $196.20  
  7 purchase totals = $1,285.55       $1,396.0688   $1,396.05   $1,396.00   $1,396.10