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	$10.46	7.863%	$11.2825	$11.28	$11.30	$11.30
Purchase #2	$113.72	13.301%	$128.8459	$128.85	$128.85	$128.80
Purchase #3	$200.60	10.743%	$222.1505	$222.15	$222.15	$222.20
Purchase #4	$71.59	9.682%	$78.5213	$78.52	$78.50	$78.50
Purchase #5	$194.52	6.554%	$207.2688	$207.27	$207.25	$207.30
Purchase #6	$79.28	9.589%	$86.8822	$86.88	$86.90	$86.90
Purchase #7	$246.56	10.294%	$271.9409	$271.94	$271.95	$271.90
7 purchase totals =	$916.73		$1,006.8921	$1,006.89	$1,006.90	$1,006.90