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	$96.57	13.405%	$109.5152	$109.52	$109.50	$109.50
Purchase #2	$114.54	3.169%	$118.1698	$118.17	$118.15	$118.20
Purchase #3	$30.83	5.103%	$32.4033	$32.40	$32.40	$32.40
Purchase #4	$175.27	5.337%	$184.6242	$184.62	$184.60	$184.60
Purchase #5	$110.73	11.675%	$123.6577	$123.66	$123.65	$123.70
Purchase #6	$85.74	7.165%	$91.8833	$91.88	$91.90	$91.90
Purchase #7	$227.90	5.244%	$239.8511	$239.85	$239.85	$239.90
7 purchase totals =	$841.58		$900.1046	$900.10	$900.05	$900.20