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	$52.85	6.176%	$56.114	$56.11	$56.10	$56.10
Purchase #2	$185.53	4.545%	$193.9623	$193.96	$193.95	$194.00
Purchase #3	$215.25	12.767%	$242.731	$242.73	$242.75	$242.70
Purchase #4	$139.77	6.240%	$148.4916	$148.49	$148.50	$148.50
Purchase #5	$75.64	8.481%	$82.055	$82.06	$82.05	$82.10
Purchase #6	$51.84	4.725%	$54.2894	$54.29	$54.30	$54.30
Purchase #7	$194.46	11.321%	$216.4748	$216.47	$216.45	$216.50
7 purchase totals =	$915.34		$994.1181	$994.11	$994.10	$994.20