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	$218.82	6.770%	$233.6341	$233.63	$233.65	$233.60
Purchase #2	$36.88	6.219%	$39.1736	$39.17	$39.15	$39.20
Purchase #3	$83.33	8.271%	$90.2222	$90.22	$90.20	$90.20
Purchase #4	$245.58	3.480%	$254.1262	$254.13	$254.15	$254.10
Purchase #5	$180.91	13.492%	$205.3184	$205.32	$205.30	$205.30
Purchase #6	$162.31	4.607%	$169.7876	$169.79	$169.80	$169.80
Purchase #7	$21.68	3.602%	$22.4609	$22.46	$22.45	$22.50
7 purchase totals =	$949.51		$1,014.7230	$1,014.72	$1,014.70	$1,014.70