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	$56.69	10.251%	$62.5013	$62.50	$62.50	$62.50
Purchase #2	$95.29	4.821%	$99.8839	$99.88	$99.90	$99.90
Purchase #3	$145.95	5.434%	$153.8809	$153.88	$153.90	$153.90
Purchase #4	$99.85	5.330%	$105.172	$105.17	$105.15	$105.20
Purchase #5	$71.49	8.427%	$77.5145	$77.51	$77.50	$77.50
Purchase #6	$166.52	6.312%	$177.0307	$177.03	$177.05	$177.00
Purchase #7	$62.73	10.554%	$69.3505	$69.35	$69.35	$69.40
7 purchase totals =	$698.52		$745.3338	$745.32	$745.35	$745.40