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	$207.86	13.382%	$235.6758	$235.68	$235.70	$235.70
Purchase #2	$52.41	13.350%	$59.4067	$59.41	$59.40	$59.40
Purchase #3	$171.82	9.133%	$187.5123	$187.51	$187.50	$187.50
Purchase #4	$146.88	9.169%	$160.3474	$160.35	$160.35	$160.30
Purchase #5	$147.62	13.410%	$167.4158	$167.42	$167.40	$167.40
Purchase #6	$56.88	7.335%	$61.0521	$61.05	$61.05	$61.10
Purchase #7	$219.79	5.792%	$232.5202	$232.52	$232.50	$232.50
7 purchase totals =	$1,003.26		$1,103.9303	$1,103.94	$1,103.90	$1,103.90