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	$90.44	5.122%	$95.0723	$95.07	$95.05	$95.10
Purchase #2	$206.61	7.856%	$222.8413	$222.84	$222.85	$222.80
Purchase #3	$50.52	3.143%	$52.1078	$52.11	$52.10	$52.10
Purchase #4	$92.69	13.525%	$105.2263	$105.23	$105.25	$105.20
Purchase #5	$84.96	6.645%	$90.6056	$90.61	$90.60	$90.60
Purchase #6	$36.61	3.397%	$37.8536	$37.85	$37.85	$37.90
Purchase #7	$13.74	10.578%	$15.1934	$15.19	$15.20	$15.20
7 purchase totals =	$575.57		$618.9003	$618.90	$618.90	$618.90