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	$178.34	12.230%	$200.151	$200.15	$200.15	$200.20
Purchase #2	$240.44	4.867%	$252.1422	$252.14	$252.15	$252.10
Purchase #3	$100.74	8.316%	$109.1175	$109.12	$109.10	$109.10
Purchase #4	$149.85	8.433%	$162.4869	$162.49	$162.50	$162.50
Purchase #5	$167.87	13.403%	$190.3696	$190.37	$190.35	$190.40
Purchase #6	$141.79	3.778%	$147.1468	$147.15	$147.15	$147.10
Purchase #7	$22.53	4.653%	$23.5783	$23.58	$23.60	$23.60
7 purchase totals =	$1,001.56		$1,084.9923	$1,085.00	$1,085.00	$1,085.00