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	$117.99	8.360%	$127.854	$127.85	$127.85	$127.90
Purchase #2	$139.49	11.536%	$155.5816	$155.58	$155.60	$155.60
Purchase #3	$186.90	10.446%	$206.4236	$206.42	$206.40	$206.40
Purchase #4	$250.36	4.603%	$261.8841	$261.88	$261.90	$261.90
Purchase #5	$241.73	5.704%	$255.5183	$255.52	$255.50	$255.50
Purchase #6	$127.76	9.377%	$139.7401	$139.74	$139.75	$139.70
Purchase #7	$146.88	4.709%	$153.7966	$153.80	$153.80	$153.80
7 purchase totals =	$1,211.11		$1,300.7983	$1,300.79	$1,300.80	$1,300.80