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	$50.81	10.823%	$56.3092	$56.31	$56.30	$56.30
Purchase #2	$56.30	7.159%	$60.3305	$60.33	$60.35	$60.30
Purchase #3	$67.72	5.532%	$71.4663	$71.47	$71.45	$71.50
Purchase #4	$157.93	12.743%	$178.055	$178.06	$178.05	$178.10
Purchase #5	$199.81	13.128%	$226.0411	$226.04	$226.05	$226.00
Purchase #6	$174.56	12.518%	$196.4114	$196.41	$196.40	$196.40
Purchase #7	$55.46	4.827%	$58.1371	$58.14	$58.15	$58.10
7 purchase totals =	$762.59		$846.7506	$846.76	$846.75	$846.70