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	$43.62	5.381%	$45.9672	$45.97	$45.95	$46.00
Purchase #2	$70.46	11.763%	$78.7482	$78.75	$78.75	$78.70
Purchase #3	$70.57	13.872%	$80.3595	$80.36	$80.35	$80.40
Purchase #4	$129.99	11.430%	$144.8479	$144.85	$144.85	$144.80
Purchase #5	$113.56	12.523%	$127.7811	$127.78	$127.80	$127.80
Purchase #6	$196.99	13.173%	$222.9395	$222.94	$222.95	$222.90
Purchase #7	$39.92	5.178%	$41.9871	$41.99	$42.00	$42.00
7 purchase totals =	$665.11		$742.6305	$742.64	$742.65	$742.60