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	$41.42	12.208%	$46.4766	$46.48	$46.50	$46.50
Purchase #2	$114.61	10.363%	$126.487	$126.49	$126.50	$126.50
Purchase #3	$205.47	11.488%	$229.0744	$229.07	$229.05	$229.10
Purchase #4	$62.73	6.843%	$67.0226	$67.02	$67.00	$67.00
Purchase #5	$145.26	13.778%	$165.2739	$165.27	$165.25	$165.30
Purchase #6	$75.81	4.246%	$79.0289	$79.03	$79.05	$79.00
Purchase #7	$204.79	10.123%	$225.5209	$225.52	$225.50	$225.50
7 purchase totals =	$850.09		$938.8843	$938.88	$938.85	$938.90