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	$89.39	3.610%	$92.617	$92.62	$92.60	$92.60
Purchase #2	$64.54	13.538%	$73.2774	$73.28	$73.30	$73.30
Purchase #3	$72.71	7.415%	$78.1014	$78.10	$78.10	$78.10
Purchase #4	$163.32	9.197%	$178.3405	$178.34	$178.35	$178.30
Purchase #5	$33.42	9.233%	$36.5057	$36.51	$36.50	$36.50
Purchase #6	$230.48	10.579%	$254.8625	$254.86	$254.85	$254.90
Purchase #7	$6.95	5.747%	$7.3494	$7.35	$7.35	$7.30
7 purchase totals =	$660.81		$721.0539	$721.06	$721.05	$721.00