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	$68.45	13.315%	$77.5641	$77.56	$77.55	$77.60
Purchase #2	$81.67	12.801%	$92.1246	$92.12	$92.10	$92.10
Purchase #3	$173.52	12.856%	$195.8277	$195.83	$195.85	$195.80
Purchase #4	$62.38	4.496%	$65.1846	$65.18	$65.20	$65.20
Purchase #5	$28.50	10.362%	$31.4532	$31.45	$31.45	$31.50
Purchase #6	$198.60	4.821%	$208.1745	$208.17	$208.15	$208.20
Purchase #7	$231.86	11.386%	$258.2596	$258.26	$258.25	$258.30
7 purchase totals =	$844.98		$928.5883	$928.57	$928.55	$928.70