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	$70.37	5.636%	$74.3361	$74.34	$74.35	$74.30
Purchase #2	$125.74	6.550%	$133.976	$133.98	$134.00	$134.00
Purchase #3	$144.42	4.746%	$151.2742	$151.27	$151.25	$151.30
Purchase #4	$129.41	11.193%	$143.8949	$143.89	$143.90	$143.90
Purchase #5	$51.72	10.540%	$57.1713	$57.17	$57.15	$57.20
Purchase #6	$243.25	5.454%	$256.5169	$256.52	$256.50	$256.50
Purchase #7	$162.52	13.870%	$185.0615	$185.06	$185.05	$185.10
7 purchase totals =	$927.43		$1,002.2309	$1,002.23	$1,002.20	$1,002.30