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	$56.60	7.623%	$60.9146	$60.91	$60.90	$60.90
Purchase #2	$236.99	4.543%	$247.7565	$247.76	$247.75	$247.80
Purchase #3	$94.76	11.371%	$105.5352	$105.54	$105.55	$105.50
Purchase #4	$98.48	7.403%	$105.7705	$105.77	$105.75	$105.80
Purchase #5	$144.50	10.244%	$159.3026	$159.30	$159.30	$159.30
Purchase #6	$27.25	11.139%	$30.2854	$30.29	$30.30	$30.30
Purchase #7	$39.83	6.862%	$42.5631	$42.56	$42.55	$42.60
7 purchase totals =	$698.41		$752.1279	$752.13	$752.10	$752.20