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 $65.95   4.145%   $68.6836   $68.68   $68.70   $68.70  
  Purchase #2 $238.26   5.763%   $251.9909   $251.99   $252.00   $252.00  
  Purchase #3 $120.91   3.654%   $125.3281   $125.33   $125.35   $125.30  
  Purchase #4 $230.89   9.277%   $252.3097   $252.31   $252.30   $252.30  
  Purchase #5 $192.38   10.106%   $211.8219   $211.82   $211.80   $211.80  
  Purchase #6 $75.96   12.109%   $85.158   $85.16   $85.15   $85.20  
  Purchase #7 $126.59   8.602%   $137.4793   $137.48   $137.50   $137.50  
  7 purchase totals = $1,050.94       $1,132.7715   $1,132.77   $1,132.80   $1,132.80