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	$99.90	13.676%	$113.5623	$113.56	$113.55	$113.60
Purchase #2	$158.51	3.788%	$164.5144	$164.51	$164.50	$164.50
Purchase #3	$220.31	6.721%	$235.117	$235.12	$235.10	$235.10
Purchase #4	$53.45	9.805%	$58.6908	$58.69	$58.70	$58.70
Purchase #5	$42.71	13.127%	$48.3165	$48.32	$48.30	$48.30
Purchase #6	$138.51	13.584%	$157.3252	$157.33	$157.35	$157.30
Purchase #7	$212.28	5.353%	$223.6433	$223.64	$223.65	$223.60
7 purchase totals =	$925.67		$1,001.1695	$1,001.17	$1,001.15	$1,001.10