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	$78.83	4.518%	$82.3915	$82.39	$82.40	$82.40
Purchase #2	$142.28	7.682%	$153.2099	$153.21	$153.20	$153.20
Purchase #3	$242.86	5.301%	$255.734	$255.73	$255.75	$255.70
Purchase #4	$195.47	11.170%	$217.304	$217.30	$217.30	$217.30
Purchase #5	$39.93	11.419%	$44.4896	$44.49	$44.50	$44.50
Purchase #6	$250.58	8.205%	$271.1401	$271.14	$271.15	$271.10
Purchase #7	$113.51	12.651%	$127.8702	$127.87	$127.85	$127.90
7 purchase totals =	$1,063.46		$1,152.1393	$1,152.13	$1,152.15	$1,152.10