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	$5.87	4.702%	$6.146	$6.15	$6.15	$6.10
Purchase #2	$218.64	5.262%	$230.1448	$230.14	$230.15	$230.10
Purchase #3	$117.72	4.545%	$123.0704	$123.07	$123.05	$123.10
Purchase #4	$212.89	11.558%	$237.4958	$237.50	$237.50	$237.50
Purchase #5	$152.68	8.139%	$165.1066	$165.11	$165.10	$165.10
Purchase #6	$186.84	11.835%	$208.9525	$208.95	$208.95	$209.00
Purchase #7	$80.71	12.565%	$90.8512	$90.85	$90.85	$90.90
7 purchase totals =	$975.35		$1,061.7673	$1,061.77	$1,061.75	$1,061.80