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	$207.48	7.622%	$223.2941	$223.29	$223.30	$223.30
Purchase #2	$79.45	5.460%	$83.788	$83.79	$83.80	$83.80
Purchase #3	$15.49	13.776%	$17.6239	$17.62	$17.60	$17.60
Purchase #4	$196.58	11.852%	$219.8787	$219.88	$219.90	$219.90
Purchase #5	$102.84	9.682%	$112.797	$112.80	$112.80	$112.80
Purchase #6	$78.60	10.422%	$86.7917	$86.79	$86.80	$86.80
Purchase #7	$100.83	3.662%	$104.5224	$104.52	$104.50	$104.50
7 purchase totals =	$781.27		$848.6958	$848.69	$848.70	$848.70