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	$57.74	5.227%	$60.7581	$60.76	$60.75	$60.80
Purchase #2	$170.55	6.206%	$181.1343	$181.13	$181.15	$181.10
Purchase #3	$34.85	6.762%	$37.2066	$37.21	$37.20	$37.20
Purchase #4	$152.66	3.710%	$158.3237	$158.32	$158.30	$158.30
Purchase #5	$184.77	11.598%	$206.1996	$206.20	$206.20	$206.20
Purchase #6	$118.95	7.256%	$127.581	$127.58	$127.60	$127.60
Purchase #7	$80.86	12.217%	$90.7387	$90.74	$90.75	$90.70
7 purchase totals =	$800.38		$861.9420	$861.94	$861.95	$861.90