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	$173.55	8.469%	$188.2479	$188.25	$188.25	$188.20
Purchase #2	$73.37	11.848%	$82.0629	$82.06	$82.05	$82.10
Purchase #3	$41.35	9.197%	$45.153	$45.15	$45.15	$45.20
Purchase #4	$117.78	8.494%	$127.7842	$127.78	$127.80	$127.80
Purchase #5	$228.27	5.521%	$240.8728	$240.87	$240.85	$240.90
Purchase #6	$57.80	4.566%	$60.4391	$60.44	$60.45	$60.40
Purchase #7	$19.48	3.509%	$20.1636	$20.16	$20.15	$20.20
7 purchase totals =	$711.60		$764.7235	$764.71	$764.70	$764.80