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	$105.72	5.438%	$111.4691	$111.47	$111.45	$111.50
Purchase #2	$88.75	11.628%	$99.0699	$99.07	$99.05	$99.10
Purchase #3	$15.48	12.412%	$17.4014	$17.40	$17.40	$17.40
Purchase #4	$28.70	6.503%	$30.5664	$30.57	$30.55	$30.60
Purchase #5	$51.90	8.319%	$56.2176	$56.22	$56.20	$56.20
Purchase #6	$163.42	3.244%	$168.7213	$168.72	$168.70	$168.70
Purchase #7	$219.94	12.820%	$248.1363	$248.14	$248.15	$248.10
7 purchase totals =	$673.91		$731.5820	$731.59	$731.50	$731.60