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	$42.80	6.140%	$45.4279	$45.43	$45.45	$45.40
Purchase #2	$98.77	6.344%	$105.036	$105.04	$105.05	$105.00
Purchase #3	$165.72	10.755%	$183.5432	$183.54	$183.55	$183.50
Purchase #4	$111.82	3.505%	$115.7393	$115.74	$115.75	$115.70
Purchase #5	$249.37	11.830%	$278.8705	$278.87	$278.85	$278.90
Purchase #6	$204.31	13.259%	$231.3995	$231.40	$231.40	$231.40
Purchase #7	$105.41	6.169%	$111.9127	$111.91	$111.90	$111.90
7 purchase totals =	$978.20		$1,071.9291	$1,071.93	$1,071.95	$1,071.80