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	$226.74	9.387%	$248.0241	$248.02	$248.00	$248.00
Purchase #2	$129.73	8.623%	$140.9166	$140.92	$140.90	$140.90
Purchase #3	$140.38	4.342%	$146.4753	$146.48	$146.50	$146.50
Purchase #4	$86.97	5.627%	$91.8638	$91.86	$91.85	$91.90
Purchase #5	$205.77	12.452%	$231.3925	$231.39	$231.40	$231.40
Purchase #6	$90.36	11.478%	$100.7315	$100.73	$100.75	$100.70
Purchase #7	$183.37	11.824%	$205.0517	$205.05	$205.05	$205.10
7 purchase totals =	$1,063.32		$1,164.4555	$1,164.45	$1,164.45	$1,164.50