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	$248.69	3.188%	$256.6182	$256.62	$256.60	$256.60
Purchase #2	$148.31	13.275%	$167.9982	$168.00	$168.00	$168.00
Purchase #3	$213.36	4.725%	$223.4413	$223.44	$223.45	$223.40
Purchase #4	$122.64	9.260%	$133.9965	$134.00	$134.00	$134.00
Purchase #5	$158.57	4.163%	$165.1713	$165.17	$165.15	$165.20
Purchase #6	$169.50	10.460%	$187.2297	$187.23	$187.25	$187.20
Purchase #7	$160.62	3.106%	$165.6089	$165.61	$165.60	$165.60
7 purchase totals =	$1,221.69		$1,300.0641	$1,300.07	$1,300.05	$1,300.00