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	$111.45	4.432%	$116.3895	$116.39	$116.40	$116.40
Purchase #2	$131.89	9.412%	$144.3035	$144.30	$144.30	$144.30
Purchase #3	$157.40	5.489%	$166.0397	$166.04	$166.05	$166.00
Purchase #4	$59.98	11.490%	$66.8717	$66.87	$66.85	$66.90
Purchase #5	$222.67	9.178%	$243.1067	$243.11	$243.10	$243.10
Purchase #6	$191.57	10.352%	$211.4013	$211.40	$211.40	$211.40
Purchase #7	$60.51	6.819%	$64.6362	$64.64	$64.65	$64.60
7 purchase totals =	$935.47		$1,012.7486	$1,012.75	$1,012.75	$1,012.70