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	$130.30	9.238%	$142.3371	$142.34	$142.35	$142.30
Purchase #2	$15.74	11.429%	$17.5389	$17.54	$17.55	$17.50
Purchase #3	$51.34	6.536%	$54.6956	$54.70	$54.70	$54.70
Purchase #4	$158.92	9.824%	$174.5323	$174.53	$174.55	$174.50
Purchase #5	$61.52	6.133%	$65.293	$65.29	$65.30	$65.30
Purchase #6	$176.28	5.498%	$185.9719	$185.97	$185.95	$186.00
Purchase #7	$81.88	10.157%	$90.1966	$90.20	$90.20	$90.20
7 purchase totals =	$675.98		$730.5654	$730.57	$730.60	$730.50