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	$248.34	8.581%	$269.6501	$269.65	$269.65	$269.70
Purchase #2	$198.46	9.208%	$216.7342	$216.73	$216.75	$216.70
Purchase #3	$111.60	10.491%	$123.308	$123.31	$123.30	$123.30
Purchase #4	$177.78	10.689%	$196.7829	$196.78	$196.80	$196.80
Purchase #5	$83.50	6.788%	$89.168	$89.17	$89.15	$89.20
Purchase #6	$105.26	10.505%	$116.3176	$116.32	$116.30	$116.30
Purchase #7	$108.89	10.364%	$120.1754	$120.18	$120.20	$120.20
7 purchase totals =	$1,033.83		$1,132.1362	$1,132.14	$1,132.15	$1,132.20