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	$152.57	10.702%	$168.898	$168.90	$168.90	$168.90
Purchase #2	$162.82	9.420%	$178.1576	$178.16	$178.15	$178.20
Purchase #3	$127.57	13.396%	$144.6593	$144.66	$144.65	$144.70
Purchase #4	$55.48	9.319%	$60.6502	$60.65	$60.65	$60.70
Purchase #5	$66.31	6.268%	$70.4663	$70.47	$70.45	$70.50
Purchase #6	$163.75	5.295%	$172.4206	$172.42	$172.40	$172.40
Purchase #7	$250.49	12.479%	$281.7486	$281.75	$281.75	$281.70
7 purchase totals =	$978.99		$1,077.0006	$1,077.01	$1,076.95	$1,077.10