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	$144.55	5.118%	$151.9481	$151.95	$151.95	$151.90
Purchase #2	$39.69	11.717%	$44.3405	$44.34	$44.35	$44.30
Purchase #3	$111.91	6.219%	$118.8697	$118.87	$118.85	$118.90
Purchase #4	$10.97	7.436%	$11.7857	$11.79	$11.80	$11.80
Purchase #5	$61.25	7.529%	$65.8615	$65.86	$65.85	$65.90
Purchase #6	$37.75	4.427%	$39.4212	$39.42	$39.40	$39.40
Purchase #7	$89.49	7.689%	$96.3709	$96.37	$96.35	$96.40
7 purchase totals =	$495.61		$528.5976	$528.60	$528.55	$528.60