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	$142.45	10.506%	$157.4158	$157.42	$157.40	$157.40
Purchase #2	$24.73	13.783%	$28.1385	$28.14	$28.15	$28.10
Purchase #3	$89.45	13.399%	$101.4354	$101.44	$101.45	$101.40
Purchase #4	$92.33	4.733%	$96.7	$96.70	$96.70	$96.70
Purchase #5	$162.86	6.140%	$172.8596	$172.86	$172.85	$172.90
Purchase #6	$158.38	3.794%	$164.3889	$164.39	$164.40	$164.40
Purchase #7	$42.51	13.569%	$48.2782	$48.28	$48.30	$48.30
7 purchase totals =	$712.71		$769.2164	$769.23	$769.25	$769.20