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	$89.66	7.845%	$96.6938	$96.69	$96.70	$96.70
Purchase #2	$238.45	6.708%	$254.4452	$254.45	$254.45	$254.40
Purchase #3	$146.84	6.849%	$156.8971	$156.90	$156.90	$156.90
Purchase #4	$250.41	5.534%	$264.2677	$264.27	$264.25	$264.30
Purchase #5	$58.31	11.696%	$65.1299	$65.13	$65.15	$65.10
Purchase #6	$121.98	4.515%	$127.4874	$127.49	$127.50	$127.50
Purchase #7	$53.46	4.441%	$55.8342	$55.83	$55.85	$55.80
7 purchase totals =	$959.11		$1,020.7553	$1,020.76	$1,020.80	$1,020.70