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	$77.94	10.478%	$86.1066	$86.11	$86.10	$86.10
Purchase #2	$106.35	13.731%	$120.9529	$120.95	$120.95	$121.00
Purchase #3	$86.87	6.185%	$92.2429	$92.24	$92.25	$92.20
Purchase #4	$33.27	10.643%	$36.8109	$36.81	$36.80	$36.80
Purchase #5	$163.58	10.404%	$180.5989	$180.60	$180.60	$180.60
Purchase #6	$49.50	12.846%	$55.8588	$55.86	$55.85	$55.90
Purchase #7	$99.56	12.372%	$111.8776	$111.88	$111.90	$111.90
7 purchase totals =	$617.07		$684.4486	$684.45	$684.45	$684.50