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	$214.51	10.722%	$237.5098	$237.51	$237.50	$237.50
Purchase #2	$37.30	9.806%	$40.9576	$40.96	$40.95	$41.00
Purchase #3	$108.35	3.113%	$111.7229	$111.72	$111.70	$111.70
Purchase #4	$91.81	12.419%	$103.2119	$103.21	$103.20	$103.20
Purchase #5	$167.49	8.394%	$181.5491	$181.55	$181.55	$181.50
Purchase #6	$104.35	3.707%	$108.2183	$108.22	$108.20	$108.20
Purchase #7	$103.70	5.735%	$109.6472	$109.65	$109.65	$109.60
7 purchase totals =	$827.51		$892.8168	$892.82	$892.75	$892.70