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	$144.67	9.330%	$158.1677	$158.17	$158.15	$158.20
Purchase #2	$54.60	5.818%	$57.7766	$57.78	$57.80	$57.80
Purchase #3	$39.80	13.149%	$45.0333	$45.03	$45.05	$45.00
Purchase #4	$123.57	3.332%	$127.6874	$127.69	$127.70	$127.70
Purchase #5	$52.81	11.359%	$58.8087	$58.81	$58.80	$58.80
Purchase #6	$45.99	6.355%	$48.9127	$48.91	$48.90	$48.90
Purchase #7	$103.93	11.510%	$115.8923	$115.89	$115.90	$115.90
7 purchase totals =	$565.37		$612.2787	$612.28	$612.30	$612.30