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	$92.29	12.574%	$103.8945	$103.89	$103.90	$103.90
Purchase #2	$236.72	13.643%	$269.0157	$269.02	$269.00	$269.00
Purchase #3	$43.80	13.163%	$49.5654	$49.57	$49.55	$49.60
Purchase #4	$52.57	4.409%	$54.8878	$54.89	$54.90	$54.90
Purchase #5	$58.84	13.188%	$66.5998	$66.60	$66.60	$66.60
Purchase #6	$60.76	6.469%	$64.6906	$64.69	$64.70	$64.70
Purchase #7	$112.75	12.215%	$126.5224	$126.52	$126.50	$126.50
7 purchase totals =	$657.73		$735.1762	$735.18	$735.15	$735.20