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	$106.83	6.592%	$113.8722	$113.87	$113.85	$113.90
Purchase #2	$248.91	3.133%	$256.7084	$256.71	$256.70	$256.70
Purchase #3	$158.44	4.179%	$165.0612	$165.06	$165.05	$165.10
Purchase #4	$104.27	4.689%	$109.1592	$109.16	$109.15	$109.20
Purchase #5	$25.67	8.495%	$27.8507	$27.85	$27.85	$27.90
Purchase #6	$119.51	10.865%	$132.4948	$132.49	$132.50	$132.50
Purchase #7	$164.99	9.373%	$180.4545	$180.45	$180.45	$180.50
7 purchase totals =	$928.62		$985.6010	$985.59	$985.55	$985.80