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	$216.35	11.584%	$241.412	$241.41	$241.40	$241.40
Purchase #2	$126.29	13.804%	$143.7231	$143.72	$143.70	$143.70
Purchase #3	$71.29	13.646%	$81.0182	$81.02	$81.00	$81.00
Purchase #4	$52.82	3.760%	$54.806	$54.81	$54.80	$54.80
Purchase #5	$82.51	11.304%	$91.8369	$91.84	$91.85	$91.80
Purchase #6	$145.92	13.716%	$165.9344	$165.93	$165.95	$165.90
Purchase #7	$50.25	3.627%	$52.0726	$52.07	$52.05	$52.10
7 purchase totals =	$745.43		$830.8032	$830.80	$830.75	$830.70