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	$67.30	4.503%	$70.3305	$70.33	$70.35	$70.30
Purchase #2	$214.42	10.830%	$237.6417	$237.64	$237.65	$237.60
Purchase #3	$198.67	4.640%	$207.8883	$207.89	$207.90	$207.90
Purchase #4	$120.98	5.352%	$127.4548	$127.45	$127.45	$127.50
Purchase #5	$82.55	5.279%	$86.9078	$86.91	$86.90	$86.90
Purchase #6	$61.27	9.245%	$66.9344	$66.93	$66.95	$66.90
Purchase #7	$9.49	9.850%	$10.4248	$10.42	$10.40	$10.40
7 purchase totals =	$754.68		$807.5823	$807.57	$807.60	$807.50