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	$238.65	12.760%	$269.1017	$269.10	$269.10	$269.10
Purchase #2	$196.72	7.687%	$211.8419	$211.84	$211.85	$211.80
Purchase #3	$177.64	6.161%	$188.5844	$188.58	$188.60	$188.60
Purchase #4	$98.89	4.601%	$103.4399	$103.44	$103.45	$103.40
Purchase #5	$142.35	8.114%	$153.9003	$153.90	$153.90	$153.90
Purchase #6	$229.71	11.108%	$255.2262	$255.23	$255.25	$255.20
Purchase #7	$126.45	4.505%	$132.1466	$132.15	$132.15	$132.10
7 purchase totals =	$1,210.41		$1,314.2410	$1,314.24	$1,314.30	$1,314.10