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	$103.30	4.634%	$108.0869	$108.09	$108.10	$108.10
Purchase #2	$18.83	9.333%	$20.5874	$20.59	$20.60	$20.60
Purchase #3	$129.78	11.205%	$144.3218	$144.32	$144.30	$144.30
Purchase #4	$52.83	8.172%	$57.1473	$57.15	$57.15	$57.10
Purchase #5	$171.31	13.492%	$194.4231	$194.42	$194.40	$194.40
Purchase #6	$103.27	10.556%	$114.1712	$114.17	$114.15	$114.20
Purchase #7	$101.88	6.612%	$108.6163	$108.62	$108.60	$108.60
7 purchase totals =	$681.20		$747.3540	$747.36	$747.30	$747.30