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	$46.66	12.315%	$52.4062	$52.41	$52.40	$52.40
Purchase #2	$115.31	10.374%	$127.2723	$127.27	$127.25	$127.30
Purchase #3	$200.86	5.530%	$211.9676	$211.97	$211.95	$212.00
Purchase #4	$45.31	3.421%	$46.8601	$46.86	$46.85	$46.90
Purchase #5	$15.76	3.658%	$16.3365	$16.34	$16.35	$16.30
Purchase #6	$132.78	10.524%	$146.7538	$146.75	$146.75	$146.80
Purchase #7	$73.29	7.359%	$78.6834	$78.68	$78.70	$78.70
7 purchase totals =	$629.97		$680.2799	$680.28	$680.25	$680.40