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	$192.58	9.713%	$211.2853	$211.29	$211.30	$211.30
Purchase #2	$61.40	4.208%	$63.9837	$63.98	$64.00	$64.00
Purchase #3	$241.94	5.247%	$254.6346	$254.63	$254.65	$254.60
Purchase #4	$178.25	10.458%	$196.8914	$196.89	$196.90	$196.90
Purchase #5	$46.33	5.528%	$48.8911	$48.89	$48.90	$48.90
Purchase #6	$204.50	4.702%	$214.1156	$214.12	$214.10	$214.10
Purchase #7	$152.48	4.332%	$159.0854	$159.09	$159.10	$159.10
7 purchase totals =	$1,077.48		$1,148.8871	$1,148.89	$1,148.95	$1,148.90