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	$106.87	4.207%	$111.366	$111.37	$111.35	$111.40
Purchase #2	$72.36	7.562%	$77.8319	$77.83	$77.85	$77.80
Purchase #3	$163.66	10.385%	$180.6561	$180.66	$180.65	$180.70
Purchase #4	$78.59	13.182%	$88.9497	$88.95	$88.95	$88.90
Purchase #5	$100.59	3.816%	$104.4285	$104.43	$104.45	$104.40
Purchase #6	$162.96	6.338%	$173.2884	$173.29	$173.30	$173.30
Purchase #7	$166.88	6.743%	$178.1327	$178.13	$178.15	$178.10
7 purchase totals =	$851.91		$914.6533	$914.66	$914.70	$914.60