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	$147.40	13.390%	$167.1369	$167.14	$167.15	$167.10
Purchase #2	$28.60	4.467%	$29.8776	$29.88	$29.90	$29.90
Purchase #3	$38.27	12.187%	$42.934	$42.93	$42.95	$42.90
Purchase #4	$46.78	8.172%	$50.6029	$50.60	$50.60	$50.60
Purchase #5	$57.79	11.481%	$64.4249	$64.42	$64.40	$64.40
Purchase #6	$103.61	6.754%	$110.6078	$110.61	$110.60	$110.60
Purchase #7	$58.64	9.318%	$64.1041	$64.10	$64.10	$64.10
7 purchase totals =	$481.09		$529.6882	$529.68	$529.70	$529.60