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	$217.53	3.575%	$225.3067	$225.31	$225.30	$225.30
Purchase #2	$169.83	3.792%	$176.27	$176.27	$176.25	$176.30
Purchase #3	$97.91	13.653%	$111.2777	$111.28	$111.30	$111.30
Purchase #4	$104.95	9.155%	$114.5582	$114.56	$114.55	$114.60
Purchase #5	$138.33	9.537%	$151.5225	$151.52	$151.50	$151.50
Purchase #6	$85.74	5.820%	$90.7301	$90.73	$90.75	$90.70
Purchase #7	$234.84	10.392%	$259.2446	$259.24	$259.25	$259.20
7 purchase totals =	$1,049.13		$1,128.9098	$1,128.91	$1,128.90	$1,128.90