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	$99.42	9.454%	$108.8192	$108.82	$108.80	$108.80
Purchase #2	$114.83	6.872%	$122.7211	$122.72	$122.70	$122.70
Purchase #3	$200.42	11.192%	$222.851	$222.85	$222.85	$222.90
Purchase #4	$226.64	10.628%	$250.7273	$250.73	$250.75	$250.70
Purchase #5	$228.91	12.428%	$257.3589	$257.36	$257.35	$257.40
Purchase #6	$123.53	3.130%	$127.3965	$127.40	$127.40	$127.40
Purchase #7	$103.67	5.257%	$109.1199	$109.12	$109.10	$109.10
7 purchase totals =	$1,097.42		$1,198.9939	$1,199.00	$1,198.95	$1,199.00