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	$250.27	5.584%	$264.2451	$264.25	$264.25	$264.20
Purchase #2	$136.37	4.596%	$142.6376	$142.64	$142.65	$142.60
Purchase #3	$139.59	7.496%	$150.0537	$150.05	$150.05	$150.10
Purchase #4	$149.43	11.472%	$166.5726	$166.57	$166.55	$166.60
Purchase #5	$12.87	13.312%	$14.5833	$14.58	$14.60	$14.60
Purchase #6	$217.84	7.309%	$233.7619	$233.76	$233.75	$233.80
Purchase #7	$86.50	4.816%	$90.6658	$90.67	$90.65	$90.70
7 purchase totals =	$992.87		$1,062.5200	$1,062.52	$1,062.50	$1,062.60