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	$215.69	9.245%	$235.6305	$235.63	$235.65	$235.60
Purchase #2	$19.52	7.299%	$20.9448	$20.94	$20.95	$20.90
Purchase #3	$101.56	11.393%	$113.1307	$113.13	$113.15	$113.10
Purchase #4	$94.88	5.218%	$99.8308	$99.83	$99.85	$99.80
Purchase #5	$44.57	10.229%	$49.1291	$49.13	$49.15	$49.10
Purchase #6	$134.32	6.746%	$143.3812	$143.38	$143.40	$143.40
Purchase #7	$212.56	12.160%	$238.4073	$238.41	$238.40	$238.40
7 purchase totals =	$823.10		$900.4544	$900.45	$900.55	$900.30