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	$169.59	5.823%	$179.4652	$179.47	$179.45	$179.50
Purchase #2	$60.35	9.139%	$65.8654	$65.87	$65.85	$65.90
Purchase #3	$45.31	7.636%	$48.7699	$48.77	$48.75	$48.80
Purchase #4	$83.45	11.305%	$92.884	$92.88	$92.90	$92.90
Purchase #5	$23.40	7.858%	$25.2388	$25.24	$25.25	$25.20
Purchase #6	$50.89	12.816%	$57.4121	$57.41	$57.40	$57.40
Purchase #7	$222.25	12.446%	$249.9112	$249.91	$249.90	$249.90
7 purchase totals =	$655.24		$719.5466	$719.55	$719.50	$719.60