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	$96.30	11.636%	$107.5055	$107.51	$107.50	$107.50
Purchase #2	$78.59	4.474%	$82.1061	$82.11	$82.10	$82.10
Purchase #3	$225.72	3.545%	$233.7218	$233.72	$233.70	$233.70
Purchase #4	$141.58	10.451%	$156.3765	$156.38	$156.40	$156.40
Purchase #5	$202.33	7.435%	$217.3732	$217.37	$217.35	$217.40
Purchase #6	$229.51	5.146%	$241.3206	$241.32	$241.30	$241.30
Purchase #7	$140.92	7.627%	$151.668	$151.67	$151.65	$151.70
7 purchase totals =	$1,114.95		$1,190.0717	$1,190.08	$1,190.00	$1,190.10