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	$160.79	4.526%	$168.0674	$168.07	$168.05	$168.10
Purchase #2	$28.25	13.153%	$31.9657	$31.97	$31.95	$32.00
Purchase #3	$196.55	9.768%	$215.749	$215.75	$215.75	$215.70
Purchase #4	$129.80	5.218%	$136.573	$136.57	$136.55	$136.60
Purchase #5	$118.89	5.808%	$125.7951	$125.80	$125.80	$125.80
Purchase #6	$52.93	12.356%	$59.47	$59.47	$59.45	$59.50
Purchase #7	$67.45	5.109%	$70.896	$70.90	$70.90	$70.90
7 purchase totals =	$754.66		$808.5162	$808.53	$808.45	$808.60