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	$9.66	9.527%	$10.5803	$10.58	$10.60	$10.60
Purchase #2	$84.74	4.430%	$88.494	$88.49	$88.50	$88.50
Purchase #3	$82.38	6.334%	$87.5979	$87.60	$87.60	$87.60
Purchase #4	$91.75	10.211%	$101.1186	$101.12	$101.10	$101.10
Purchase #5	$15.71	11.460%	$17.5104	$17.51	$17.50	$17.50
Purchase #6	$109.87	12.391%	$123.484	$123.48	$123.50	$123.50
Purchase #7	$34.46	7.538%	$37.0576	$37.06	$37.05	$37.10
7 purchase totals =	$428.57		$465.8428	$465.84	$465.85	$465.90