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	$112.32	13.368%	$127.3349	$127.33	$127.35	$127.30
Purchase #2	$165.64	4.188%	$172.577	$172.58	$172.60	$172.60
Purchase #3	$42.61	11.570%	$47.54	$47.54	$47.55	$47.50
Purchase #4	$113.51	10.569%	$125.5069	$125.51	$125.50	$125.50
Purchase #5	$151.70	11.856%	$169.6856	$169.69	$169.70	$169.70
Purchase #6	$241.64	9.588%	$264.8084	$264.81	$264.80	$264.80
Purchase #7	$146.64	12.808%	$165.4217	$165.42	$165.40	$165.40
7 purchase totals =	$974.06		$1,072.8745	$1,072.88	$1,072.90	$1,072.80