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	$219.49	8.696%	$238.5769	$238.58	$238.60	$238.60
Purchase #2	$188.40	8.834%	$205.0433	$205.04	$205.05	$205.00
Purchase #3	$234.78	3.726%	$243.5279	$243.53	$243.55	$243.50
Purchase #4	$172.62	10.274%	$190.355	$190.36	$190.35	$190.40
Purchase #5	$55.33	6.394%	$58.8678	$58.87	$58.85	$58.90
Purchase #6	$39.46	3.173%	$40.7121	$40.71	$40.70	$40.70
Purchase #7	$84.64	11.812%	$94.6377	$94.64	$94.65	$94.60
7 purchase totals =	$994.72		$1,071.7207	$1,071.73	$1,071.75	$1,071.70