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	$75.61	7.272%	$81.1084	$81.11	$81.10	$81.10
Purchase #2	$209.38	5.499%	$220.8938	$220.89	$220.90	$220.90
Purchase #3	$152.30	13.762%	$173.2595	$173.26	$173.25	$173.30
Purchase #4	$62.86	4.452%	$65.6585	$65.66	$65.65	$65.70
Purchase #5	$208.34	7.235%	$223.4134	$223.41	$223.40	$223.40
Purchase #6	$162.98	5.705%	$172.278	$172.28	$172.30	$172.30
Purchase #7	$121.94	4.733%	$127.7114	$127.71	$127.70	$127.70
7 purchase totals =	$993.41		$1,064.3230	$1,064.32	$1,064.30	$1,064.40