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	$157.34	6.506%	$167.5765	$167.58	$167.60	$167.60
Purchase #2	$150.96	9.604%	$165.4582	$165.46	$165.45	$165.50
Purchase #3	$159.90	10.363%	$176.4704	$176.47	$176.45	$176.50
Purchase #4	$165.47	5.194%	$174.0645	$174.06	$174.05	$174.10
Purchase #5	$96.37	11.869%	$107.8082	$107.81	$107.80	$107.80
Purchase #6	$11.65	7.321%	$12.5029	$12.50	$12.50	$12.50
Purchase #7	$236.77	8.849%	$257.7218	$257.72	$257.70	$257.70
7 purchase totals =	$978.46		$1,061.6025	$1,061.60	$1,061.55	$1,061.70