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	$94.61	4.831%	$99.1806	$99.18	$99.20	$99.20
Purchase #2	$162.94	8.581%	$176.9219	$176.92	$176.90	$176.90
Purchase #3	$138.69	10.122%	$152.7282	$152.73	$152.75	$152.70
Purchase #4	$10.76	4.857%	$11.2826	$11.28	$11.30	$11.30
Purchase #5	$208.37	10.148%	$229.5154	$229.52	$229.50	$229.50
Purchase #6	$18.42	4.742%	$19.2935	$19.29	$19.30	$19.30
Purchase #7	$108.25	5.237%	$113.9191	$113.92	$113.90	$113.90
7 purchase totals =	$742.04		$802.8413	$802.84	$802.85	$802.80