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	$56.89	13.818%	$64.7511	$64.75	$64.75	$64.80
Purchase #2	$187.90	4.806%	$196.9305	$196.93	$196.95	$196.90
Purchase #3	$207.78	3.431%	$214.9089	$214.91	$214.90	$214.90
Purchase #4	$166.89	3.130%	$172.1137	$172.11	$172.10	$172.10
Purchase #5	$43.86	3.577%	$45.4289	$45.43	$45.45	$45.40
Purchase #6	$45.98	10.498%	$50.807	$50.81	$50.80	$50.80
Purchase #7	$63.76	5.630%	$67.3497	$67.35	$67.35	$67.30
7 purchase totals =	$773.06		$812.2898	$812.29	$812.30	$812.20