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	$223.28	7.629%	$240.314	$240.31	$240.30	$240.30
Purchase #2	$93.67	10.697%	$103.6899	$103.69	$103.70	$103.70
Purchase #3	$53.65	3.438%	$55.4945	$55.49	$55.50	$55.50
Purchase #4	$134.35	13.133%	$151.9942	$151.99	$152.00	$152.00
Purchase #5	$105.37	11.430%	$117.4138	$117.41	$117.40	$117.40
Purchase #6	$165.56	4.308%	$172.6923	$172.69	$172.70	$172.70
Purchase #7	$229.63	12.294%	$257.8607	$257.86	$257.85	$257.90
7 purchase totals =	$1,005.51		$1,099.4594	$1,099.44	$1,099.45	$1,099.50