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	$146.36	5.165%	$153.9195	$153.92	$153.90	$153.90
Purchase #2	$43.28	7.279%	$46.4304	$46.43	$46.45	$46.40
Purchase #3	$29.25	12.518%	$32.9115	$32.91	$32.90	$32.90
Purchase #4	$167.97	6.323%	$178.5907	$178.59	$178.60	$178.60
Purchase #5	$82.95	6.532%	$88.3683	$88.37	$88.35	$88.40
Purchase #6	$19.52	4.105%	$20.3213	$20.32	$20.30	$20.30
Purchase #7	$181.46	6.159%	$192.6361	$192.64	$192.65	$192.60
7 purchase totals =	$670.79		$713.1778	$713.18	$713.15	$713.10