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	$169.28	12.505%	$190.4485	$190.45	$190.45	$190.40
Purchase #2	$185.32	10.612%	$204.9862	$204.99	$205.00	$205.00
Purchase #3	$246.88	11.517%	$275.3132	$275.31	$275.30	$275.30
Purchase #4	$239.40	13.457%	$271.6161	$271.62	$271.60	$271.60
Purchase #5	$34.31	3.298%	$35.4415	$35.44	$35.45	$35.40
Purchase #6	$220.78	12.485%	$248.3444	$248.34	$248.35	$248.30
Purchase #7	$92.62	13.831%	$105.4303	$105.43	$105.45	$105.40
7 purchase totals =	$1,188.59		$1,331.5802	$1,331.58	$1,331.60	$1,331.40