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	$41.83	8.411%	$45.3483	$45.35	$45.35	$45.30
Purchase #2	$131.33	6.514%	$139.8848	$139.88	$139.90	$139.90
Purchase #3	$223.42	5.156%	$234.9395	$234.94	$234.95	$234.90
Purchase #4	$158.95	8.472%	$172.4162	$172.42	$172.40	$172.40
Purchase #5	$189.51	11.752%	$211.7812	$211.78	$211.80	$211.80
Purchase #6	$138.85	7.658%	$149.4831	$149.48	$149.50	$149.50
Purchase #7	$48.72	4.632%	$50.9767	$50.98	$51.00	$51.00
7 purchase totals =	$932.61		$1,004.8298	$1,004.83	$1,004.90	$1,004.80