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	$233.61	10.771%	$258.7721	$258.77	$258.75	$258.80
Purchase #2	$147.41	4.584%	$154.1673	$154.17	$154.15	$154.20
Purchase #3	$100.44	13.355%	$113.8538	$113.85	$113.85	$113.90
Purchase #4	$118.44	5.210%	$124.6107	$124.61	$124.60	$124.60
Purchase #5	$155.71	6.145%	$165.2784	$165.28	$165.30	$165.30
Purchase #6	$167.30	3.557%	$173.2509	$173.25	$173.25	$173.30
Purchase #7	$93.71	13.122%	$106.0066	$106.01	$106.00	$106.00
7 purchase totals =	$1,016.62		$1,095.9398	$1,095.94	$1,095.90	$1,096.10