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	$127.92	3.749%	$132.7157	$132.72	$132.70	$132.70
Purchase #2	$65.55	7.766%	$70.6406	$70.64	$70.65	$70.60
Purchase #3	$27.98	5.260%	$29.4517	$29.45	$29.45	$29.50
Purchase #4	$238.87	7.125%	$255.8895	$255.89	$255.90	$255.90
Purchase #5	$83.38	7.264%	$89.4367	$89.44	$89.45	$89.40
Purchase #6	$155.50	8.215%	$168.2743	$168.27	$168.25	$168.30
Purchase #7	$162.27	11.752%	$181.34	$181.34	$181.35	$181.30
7 purchase totals =	$861.47		$927.7485	$927.75	$927.75	$927.70