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	$184.39	6.573%	$196.51	$196.51	$196.50	$196.50
Purchase #2	$127.62	11.170%	$141.8752	$141.88	$141.90	$141.90
Purchase #3	$54.36	12.176%	$60.9789	$60.98	$61.00	$61.00
Purchase #4	$148.30	11.373%	$165.1662	$165.17	$165.15	$165.20
Purchase #5	$158.62	7.221%	$170.074	$170.07	$170.05	$170.10
Purchase #6	$186.67	12.694%	$210.3659	$210.37	$210.35	$210.40
Purchase #7	$150.72	5.114%	$158.4278	$158.43	$158.45	$158.40
7 purchase totals =	$1,010.68		$1,103.3980	$1,103.41	$1,103.40	$1,103.50