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	$131.43	12.487%	$147.8417	$147.84	$147.85	$147.80
Purchase #2	$160.59	4.402%	$167.6592	$167.66	$167.65	$167.70
Purchase #3	$17.98	12.561%	$20.2385	$20.24	$20.25	$20.20
Purchase #4	$172.45	6.434%	$183.5454	$183.55	$183.55	$183.50
Purchase #5	$240.40	3.152%	$247.9774	$247.98	$248.00	$248.00
Purchase #6	$148.59	9.495%	$162.6986	$162.70	$162.70	$162.70
Purchase #7	$35.67	5.389%	$37.5923	$37.59	$37.60	$37.60
7 purchase totals =	$907.11		$967.5531	$967.56	$967.60	$967.50