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	$223.69	13.543%	$253.9843	$253.98	$254.00	$254.00
Purchase #2	$108.66	7.367%	$116.665	$116.67	$116.65	$116.70
Purchase #3	$222.39	6.569%	$236.9988	$237.00	$237.00	$237.00
Purchase #4	$74.88	7.848%	$80.7566	$80.76	$80.75	$80.80
Purchase #5	$211.70	10.811%	$234.5869	$234.59	$234.60	$234.60
Purchase #6	$57.91	3.374%	$59.8639	$59.86	$59.85	$59.90
Purchase #7	$57.56	3.471%	$59.5579	$59.56	$59.55	$59.60
7 purchase totals =	$956.79		$1,042.4134	$1,042.42	$1,042.40	$1,042.60