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	$133.67	13.249%	$151.3799	$151.38	$151.40	$151.40
Purchase #2	$118.53	7.855%	$127.8405	$127.84	$127.85	$127.80
Purchase #3	$114.86	9.102%	$125.3146	$125.31	$125.30	$125.30
Purchase #4	$234.91	5.416%	$247.6327	$247.63	$247.65	$247.60
Purchase #5	$104.28	4.653%	$109.1321	$109.13	$109.15	$109.10
Purchase #6	$153.72	11.200%	$170.9366	$170.94	$170.95	$170.90
Purchase #7	$158.34	6.256%	$168.2458	$168.25	$168.25	$168.20
7 purchase totals =	$1,018.31		$1,100.4822	$1,100.48	$1,100.55	$1,100.30