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	$146.87	7.606%	$158.0409	$158.04	$158.05	$158.00
Purchase #2	$94.59	7.481%	$101.6663	$101.67	$101.65	$101.70
Purchase #3	$47.40	6.351%	$50.4104	$50.41	$50.40	$50.40
Purchase #4	$42.27	8.328%	$45.7902	$45.79	$45.80	$45.80
Purchase #5	$77.54	11.491%	$86.4501	$86.45	$86.45	$86.50
Purchase #6	$149.61	3.343%	$154.6115	$154.61	$154.60	$154.60
Purchase #7	$34.63	8.352%	$37.5223	$37.52	$37.50	$37.50
7 purchase totals =	$592.91		$634.4917	$634.49	$634.45	$634.50