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	$245.62	6.846%	$262.4351	$262.44	$262.45	$262.40
Purchase #2	$238.67	4.408%	$249.1906	$249.19	$249.20	$249.20
Purchase #3	$102.40	13.565%	$116.2906	$116.29	$116.30	$116.30
Purchase #4	$72.41	11.429%	$80.6857	$80.69	$80.70	$80.70
Purchase #5	$34.86	8.414%	$37.7931	$37.79	$37.80	$37.80
Purchase #6	$179.72	5.117%	$188.9163	$188.92	$188.90	$188.90
Purchase #7	$193.80	7.757%	$208.8331	$208.83	$208.85	$208.80
7 purchase totals =	$1,067.48		$1,144.1445	$1,144.15	$1,144.20	$1,144.10