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	$192.27	3.535%	$199.0667	$199.07	$199.05	$199.10
Purchase #2	$60.89	7.733%	$65.5986	$65.60	$65.60	$65.60
Purchase #3	$220.57	4.166%	$229.7589	$229.76	$229.75	$229.80
Purchase #4	$9.51	10.353%	$10.4946	$10.49	$10.50	$10.50
Purchase #5	$155.67	7.331%	$167.0822	$167.08	$167.10	$167.10
Purchase #6	$80.80	11.218%	$89.8641	$89.86	$89.85	$89.90
Purchase #7	$146.25	6.259%	$155.4038	$155.40	$155.40	$155.40
7 purchase totals =	$865.96		$917.2689	$917.26	$917.25	$917.40