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	$52.69	9.586%	$57.7409	$57.74	$57.75	$57.70
Purchase #2	$54.43	3.382%	$56.2708	$56.27	$56.25	$56.30
Purchase #3	$85.66	4.405%	$89.4333	$89.43	$89.45	$89.40
Purchase #4	$51.78	6.523%	$55.1576	$55.16	$55.15	$55.20
Purchase #5	$195.86	7.796%	$211.1292	$211.13	$211.15	$211.10
Purchase #6	$234.38	7.286%	$251.4569	$251.46	$251.45	$251.50
Purchase #7	$39.86	10.616%	$44.0915	$44.09	$44.10	$44.10
7 purchase totals =	$714.66		$765.2802	$765.28	$765.30	$765.30