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	$116.72	11.628%	$130.2922	$130.29	$130.30	$130.30
Purchase #2	$87.26	13.441%	$98.9886	$98.99	$99.00	$99.00
Purchase #3	$98.93	6.472%	$105.3327	$105.33	$105.35	$105.30
Purchase #4	$60.47	7.493%	$65.001	$65.00	$65.00	$65.00
Purchase #5	$48.89	9.650%	$53.6079	$53.61	$53.60	$53.60
Purchase #6	$60.92	5.676%	$64.3778	$64.38	$64.40	$64.40
Purchase #7	$161.44	7.689%	$173.8531	$173.85	$173.85	$173.90
7 purchase totals =	$634.63		$691.4533	$691.45	$691.50	$691.50