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	$217.62	7.283%	$233.4693	$233.47	$233.45	$233.50
Purchase #2	$222.83	5.150%	$234.3057	$234.31	$234.30	$234.30
Purchase #3	$224.47	13.572%	$254.9351	$254.94	$254.95	$254.90
Purchase #4	$139.47	3.697%	$144.6262	$144.63	$144.65	$144.60
Purchase #5	$250.72	3.420%	$259.2946	$259.29	$259.30	$259.30
Purchase #6	$208.86	9.403%	$228.4991	$228.50	$228.50	$228.50
Purchase #7	$46.70	5.414%	$49.2283	$49.23	$49.25	$49.20
7 purchase totals =	$1,310.67		$1,404.3583	$1,404.37	$1,404.40	$1,404.30