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	$97.99	13.681%	$111.396	$111.40	$111.40	$111.40
Purchase #2	$169.30	7.375%	$181.7859	$181.79	$181.80	$181.80
Purchase #3	$202.51	11.250%	$225.2924	$225.29	$225.30	$225.30
Purchase #4	$90.95	10.344%	$100.3579	$100.36	$100.35	$100.40
Purchase #5	$161.25	12.422%	$181.2805	$181.28	$181.30	$181.30
Purchase #6	$133.48	4.158%	$139.0301	$139.03	$139.05	$139.00
Purchase #7	$146.63	12.162%	$164.4631	$164.46	$164.45	$164.50
7 purchase totals =	$1,002.11		$1,103.6059	$1,103.61	$1,103.65	$1,103.70