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	$134.87	12.292%	$151.4482	$151.45	$151.45	$151.40
Purchase #2	$88.69	12.672%	$99.9288	$99.93	$99.95	$99.90
Purchase #3	$138.74	4.581%	$145.0957	$145.10	$145.10	$145.10
Purchase #4	$59.70	3.151%	$61.5811	$61.58	$61.60	$61.60
Purchase #5	$165.78	12.468%	$186.4495	$186.45	$186.45	$186.40
Purchase #6	$110.94	13.589%	$126.0156	$126.02	$126.00	$126.00
Purchase #7	$175.55	8.384%	$190.2681	$190.27	$190.25	$190.30
7 purchase totals =	$874.27		$960.7870	$960.80	$960.80	$960.70