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	$9.43	12.849%	$10.6417	$10.64	$10.65	$10.60
Purchase #2	$26.41	5.708%	$27.9175	$27.92	$27.90	$27.90
Purchase #3	$103.30	11.120%	$114.787	$114.79	$114.80	$114.80
Purchase #4	$104.84	4.713%	$109.7811	$109.78	$109.80	$109.80
Purchase #5	$123.36	11.227%	$137.2096	$137.21	$137.20	$137.20
Purchase #6	$98.49	13.239%	$111.5291	$111.53	$111.55	$111.50
Purchase #7	$160.52	8.237%	$173.742	$173.74	$173.75	$173.70
7 purchase totals =	$626.35		$685.6080	$685.61	$685.65	$685.50