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	$57.25	5.599%	$60.4554	$60.46	$60.45	$60.50
Purchase #2	$48.38	6.416%	$51.4841	$51.48	$51.50	$51.50
Purchase #3	$151.38	13.733%	$172.169	$172.17	$172.15	$172.20
Purchase #4	$27.76	4.204%	$28.927	$28.93	$28.95	$28.90
Purchase #5	$95.77	9.492%	$104.8605	$104.86	$104.85	$104.90
Purchase #6	$25.63	13.223%	$29.0191	$29.02	$29.00	$29.00
Purchase #7	$60.56	9.853%	$66.527	$66.53	$66.55	$66.50
7 purchase totals =	$466.73		$513.4421	$513.45	$513.45	$513.50