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	$89.98	7.640%	$96.8545	$96.85	$96.85	$96.90
Purchase #2	$193.81	13.248%	$219.4859	$219.49	$219.50	$219.50
Purchase #3	$49.55	4.569%	$51.8139	$51.81	$51.80	$51.80
Purchase #4	$212.73	8.857%	$231.5715	$231.57	$231.55	$231.60
Purchase #5	$10.59	5.205%	$11.1412	$11.14	$11.15	$11.10
Purchase #6	$237.96	4.122%	$247.7687	$247.77	$247.75	$247.80
Purchase #7	$222.62	8.823%	$242.2618	$242.26	$242.25	$242.30
7 purchase totals =	$1,017.24		$1,100.8975	$1,100.89	$1,100.85	$1,101.00