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	$122.97	3.505%	$127.2801	$127.28	$127.30	$127.30
Purchase #2	$172.92	10.126%	$190.4299	$190.43	$190.45	$190.40
Purchase #3	$137.69	10.735%	$152.471	$152.47	$152.45	$152.50
Purchase #4	$178.60	5.534%	$188.4837	$188.48	$188.50	$188.50
Purchase #5	$19.85	3.567%	$20.558	$20.56	$20.55	$20.60
Purchase #6	$81.39	5.863%	$86.1619	$86.16	$86.15	$86.20
Purchase #7	$182.99	10.736%	$202.6358	$202.64	$202.65	$202.60
7 purchase totals =	$896.41		$968.0204	$968.02	$968.05	$968.10