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	$192.94	11.549%	$215.2226	$215.22	$215.20	$215.20
Purchase #2	$244.56	5.864%	$258.901	$258.90	$258.90	$258.90
Purchase #3	$76.54	7.222%	$82.0677	$82.07	$82.05	$82.10
Purchase #4	$91.53	13.504%	$103.8902	$103.89	$103.90	$103.90
Purchase #5	$236.52	6.313%	$251.4515	$251.45	$251.45	$251.50
Purchase #6	$109.93	5.188%	$115.6332	$115.63	$115.65	$115.60
Purchase #7	$44.45	8.310%	$48.1438	$48.14	$48.15	$48.10
7 purchase totals =	$996.47		$1,075.3100	$1,075.30	$1,075.30	$1,075.30