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	$232.83	6.381%	$247.6869	$247.69	$247.70	$247.70
Purchase #2	$140.77	7.862%	$151.8373	$151.84	$151.85	$151.80
Purchase #3	$105.93	5.554%	$111.8134	$111.81	$111.80	$111.80
Purchase #4	$96.54	7.759%	$104.0305	$104.03	$104.05	$104.00
Purchase #5	$140.45	3.631%	$145.5497	$145.55	$145.55	$145.50
Purchase #6	$166.88	11.424%	$185.9444	$185.94	$185.95	$185.90
Purchase #7	$202.32	3.832%	$210.0729	$210.07	$210.05	$210.10
7 purchase totals =	$1,085.72		$1,156.9351	$1,156.93	$1,156.95	$1,156.80