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	$143.83	13.298%	$162.9565	$162.96	$162.95	$163.00
Purchase #2	$12.45	13.768%	$14.1641	$14.16	$14.15	$14.20
Purchase #3	$78.25	9.173%	$85.4279	$85.43	$85.45	$85.40
Purchase #4	$122.67	6.136%	$130.197	$130.20	$130.20	$130.20
Purchase #5	$122.38	6.635%	$130.4999	$130.50	$130.50	$130.50
Purchase #6	$169.92	9.317%	$185.7514	$185.75	$185.75	$185.80
Purchase #7	$141.27	10.778%	$156.4961	$156.50	$156.50	$156.50
7 purchase totals =	$790.77		$865.4929	$865.50	$865.50	$865.60