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	$87.32	9.498%	$95.6137	$95.61	$95.60	$95.60
Purchase #2	$223.90	8.722%	$243.4286	$243.43	$243.45	$243.40
Purchase #3	$224.43	13.559%	$254.8605	$254.86	$254.85	$254.90
Purchase #4	$181.83	4.442%	$189.9069	$189.91	$189.90	$189.90
Purchase #5	$130.67	12.105%	$146.4876	$146.49	$146.50	$146.50
Purchase #6	$170.30	5.110%	$179.0023	$179.00	$179.00	$179.00
Purchase #7	$20.52	5.240%	$21.5952	$21.60	$21.60	$21.60
7 purchase totals =	$1,038.97		$1,130.8948	$1,130.90	$1,130.90	$1,130.90