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	$246.83	6.345%	$262.4914	$262.49	$262.50	$262.50
Purchase #2	$96.44	4.423%	$100.7055	$100.71	$100.70	$100.70
Purchase #3	$106.91	5.427%	$112.712	$112.71	$112.70	$112.70
Purchase #4	$14.60	8.217%	$15.7997	$15.80	$15.80	$15.80
Purchase #5	$236.57	11.399%	$263.5366	$263.54	$263.55	$263.50
Purchase #6	$52.64	4.521%	$55.0199	$55.02	$55.00	$55.00
Purchase #7	$10.89	5.113%	$11.4468	$11.45	$11.45	$11.40
7 purchase totals =	$764.88		$821.7119	$821.72	$821.70	$821.60