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	$78.51	8.386%	$85.0938	$85.09	$85.10	$85.10
Purchase #2	$54.88	6.564%	$58.4823	$58.48	$58.50	$58.50
Purchase #3	$217.50	6.263%	$231.122	$231.12	$231.10	$231.10
Purchase #4	$175.90	9.496%	$192.6035	$192.60	$192.60	$192.60
Purchase #5	$38.72	13.800%	$44.0634	$44.06	$44.05	$44.10
Purchase #6	$218.37	5.559%	$230.5092	$230.51	$230.50	$230.50
Purchase #7	$229.38	4.327%	$239.3053	$239.31	$239.30	$239.30
7 purchase totals =	$1,013.26		$1,081.1795	$1,081.17	$1,081.15	$1,081.20