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	$96.49	9.113%	$105.2831	$105.28	$105.30	$105.30
Purchase #2	$71.64	11.354%	$79.774	$79.77	$79.75	$79.80
Purchase #3	$29.45	3.867%	$30.5888	$30.59	$30.60	$30.60
Purchase #4	$74.48	5.433%	$78.5265	$78.53	$78.55	$78.50
Purchase #5	$69.38	3.317%	$71.6813	$71.68	$71.70	$71.70
Purchase #6	$46.37	10.275%	$51.1345	$51.13	$51.15	$51.10
Purchase #7	$54.44	7.652%	$58.6057	$58.61	$58.60	$58.60
7 purchase totals =	$442.25		$475.5939	$475.59	$475.65	$475.60