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	$86.52	11.297%	$96.2942	$96.29	$96.30	$96.30
Purchase #2	$183.92	4.749%	$192.6544	$192.65	$192.65	$192.70
Purchase #3	$159.33	5.632%	$168.3035	$168.30	$168.30	$168.30
Purchase #4	$39.76	13.627%	$45.1781	$45.18	$45.20	$45.20
Purchase #5	$89.50	6.595%	$95.4025	$95.40	$95.40	$95.40
Purchase #6	$56.45	5.169%	$59.3679	$59.37	$59.35	$59.40
Purchase #7	$113.78	8.621%	$123.589	$123.59	$123.60	$123.60
7 purchase totals =	$729.26		$780.7896	$780.78	$780.80	$780.90