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 $206.78   4.594%   $216.2795   $216.28   $216.30   $216.30  
  Purchase #2 $24.56   7.199%   $26.3281   $26.33   $26.35   $26.30  
  Purchase #3 $181.65   10.296%   $200.3527   $200.35   $200.35   $200.40  
  Purchase #4 $193.28   10.628%   $213.8218   $213.82   $213.80   $213.80  
  Purchase #5 $26.48   10.108%   $29.1566   $29.16   $29.15   $29.20  
  Purchase #6 $246.30   6.536%   $262.3982   $262.40   $262.40   $262.40  
  Purchase #7 $91.59   4.450%   $95.6658   $95.67   $95.65   $95.70  
  7 purchase totals = $970.64       $1,044.0027   $1,044.01   $1,044.00   $1,044.10