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	$137.79	10.540%	$152.3131	$152.31	$152.30	$152.30
Purchase #2	$11.75	4.147%	$12.2373	$12.24	$12.25	$12.20
Purchase #3	$243.96	12.796%	$275.1771	$275.18	$275.20	$275.20
Purchase #4	$168.92	3.274%	$174.4504	$174.45	$174.45	$174.50
Purchase #5	$103.71	4.842%	$108.7316	$108.73	$108.75	$108.70
Purchase #6	$117.53	8.791%	$127.8621	$127.86	$127.85	$127.90
Purchase #7	$136.91	5.401%	$144.3045	$144.30	$144.30	$144.30
7 purchase totals =	$920.57		$995.0761	$995.07	$995.10	$995.10