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	$214.26	7.468%	$230.2609	$230.26	$230.25	$230.30
Purchase #2	$133.34	12.598%	$150.1382	$150.14	$150.15	$150.10
Purchase #3	$126.63	7.663%	$136.3337	$136.33	$136.35	$136.30
Purchase #4	$79.79	13.404%	$90.4851	$90.49	$90.50	$90.50
Purchase #5	$82.49	8.199%	$89.2534	$89.25	$89.25	$89.30
Purchase #6	$160.49	8.799%	$174.6115	$174.61	$174.60	$174.60
Purchase #7	$43.67	11.832%	$48.837	$48.84	$48.85	$48.80
7 purchase totals =	$840.67		$919.9198	$919.92	$919.95	$919.90