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	$241.44	5.329%	$254.3063	$254.31	$254.30	$254.30
Purchase #2	$77.28	6.552%	$82.3434	$82.34	$82.35	$82.30
Purchase #3	$95.82	11.417%	$106.7598	$106.76	$106.75	$106.80
Purchase #4	$186.67	3.523%	$193.2464	$193.25	$193.25	$193.20
Purchase #5	$239.87	10.714%	$265.5697	$265.57	$265.55	$265.60
Purchase #6	$154.62	12.261%	$173.578	$173.58	$173.60	$173.60
Purchase #7	$37.35	13.287%	$42.3127	$42.31	$42.30	$42.30
7 purchase totals =	$1,033.05		$1,118.1163	$1,118.12	$1,118.10	$1,118.10