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	$220.61	4.601%	$230.7603	$230.76	$230.75	$230.80
Purchase #2	$34.64	7.862%	$37.3634	$37.36	$37.35	$37.40
Purchase #3	$85.46	3.578%	$88.5178	$88.52	$88.50	$88.50
Purchase #4	$179.65	4.253%	$187.2905	$187.29	$187.30	$187.30
Purchase #5	$131.42	11.711%	$146.8106	$146.81	$146.80	$146.80
Purchase #6	$54.85	8.604%	$59.5693	$59.57	$59.55	$59.60
Purchase #7	$158.74	12.218%	$178.1349	$178.13	$178.15	$178.10
7 purchase totals =	$865.37		$928.4468	$928.44	$928.40	$928.50