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	$146.96	10.725%	$162.7215	$162.72	$162.70	$162.70
Purchase #2	$168.52	12.199%	$189.0778	$189.08	$189.10	$189.10
Purchase #3	$80.50	13.585%	$91.4359	$91.44	$91.45	$91.40
Purchase #4	$45.93	5.102%	$48.2733	$48.27	$48.25	$48.30
Purchase #5	$138.83	7.262%	$148.9118	$148.91	$148.90	$148.90
Purchase #6	$130.95	4.261%	$136.5298	$136.53	$136.55	$136.50
Purchase #7	$158.79	5.283%	$167.1789	$167.18	$167.20	$167.20
7 purchase totals =	$870.48		$944.1290	$944.13	$944.15	$944.10