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	$244.44	4.305%	$254.9631	$254.96	$254.95	$255.00
Purchase #2	$100.72	13.327%	$114.143	$114.14	$114.15	$114.10
Purchase #3	$242.59	8.284%	$262.6862	$262.69	$262.70	$262.70
Purchase #4	$99.69	10.260%	$109.9182	$109.92	$109.90	$109.90
Purchase #5	$38.42	11.208%	$42.7261	$42.73	$42.75	$42.70
Purchase #6	$179.85	6.339%	$191.2507	$191.25	$191.25	$191.30
Purchase #7	$210.58	11.337%	$234.4535	$234.45	$234.45	$234.50
7 purchase totals =	$1,116.29		$1,210.1408	$1,210.14	$1,210.15	$1,210.20