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	$113.99	8.688%	$123.8935	$123.89	$123.90	$123.90
Purchase #2	$118.48	10.874%	$131.3635	$131.36	$131.35	$131.40
Purchase #3	$235.95	4.786%	$247.2426	$247.24	$247.25	$247.20
Purchase #4	$96.95	3.857%	$100.6894	$100.69	$100.70	$100.70
Purchase #5	$148.90	11.216%	$165.6006	$165.60	$165.60	$165.60
Purchase #6	$151.91	3.157%	$156.7058	$156.71	$156.70	$156.70
Purchase #7	$208.60	11.838%	$233.2941	$233.29	$233.30	$233.30
7 purchase totals =	$1,074.78		$1,158.7895	$1,158.78	$1,158.80	$1,158.80