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	$139.81	13.308%	$158.4159	$158.42	$158.40	$158.40
Purchase #2	$179.91	3.299%	$185.8452	$185.85	$185.85	$185.80
Purchase #3	$172.45	3.768%	$178.9479	$178.95	$178.95	$178.90
Purchase #4	$94.76	10.380%	$104.5961	$104.60	$104.60	$104.60
Purchase #5	$152.47	8.694%	$165.7257	$165.73	$165.75	$165.70
Purchase #6	$184.41	10.799%	$204.3244	$204.32	$204.30	$204.30
Purchase #7	$164.57	3.416%	$170.1917	$170.19	$170.20	$170.20
7 purchase totals =	$1,088.38		$1,168.0469	$1,168.06	$1,168.05	$1,167.90