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	$139.53	11.608%	$155.7266	$155.73	$155.75	$155.70
Purchase #2	$112.93	13.570%	$128.2546	$128.25	$128.25	$128.30
Purchase #3	$145.52	5.355%	$153.3126	$153.31	$153.30	$153.30
Purchase #4	$227.60	11.855%	$254.582	$254.58	$254.60	$254.60
Purchase #5	$166.84	11.247%	$185.6045	$185.60	$185.60	$185.60
Purchase #6	$167.51	6.626%	$178.6092	$178.61	$178.60	$178.60
Purchase #7	$34.95	6.227%	$37.1263	$37.13	$37.15	$37.10
7 purchase totals =	$994.88		$1,093.2158	$1,093.21	$1,093.25	$1,093.20