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	$205.25	3.119%	$211.6517	$211.65	$211.65	$211.70
Purchase #2	$92.32	9.606%	$101.1883	$101.19	$101.20	$101.20
Purchase #3	$244.83	6.778%	$261.4246	$261.42	$261.40	$261.40
Purchase #4	$31.72	6.523%	$33.7891	$33.79	$33.80	$33.80
Purchase #5	$59.82	13.211%	$67.7228	$67.72	$67.70	$67.70
Purchase #6	$51.82	6.452%	$55.1634	$55.16	$55.15	$55.20
Purchase #7	$120.27	3.564%	$124.5564	$124.56	$124.55	$124.60
7 purchase totals =	$806.03		$855.4963	$855.49	$855.45	$855.60