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	$184.49	4.823%	$193.388	$193.39	$193.40	$193.40
Purchase #2	$210.71	7.472%	$226.4543	$226.45	$226.45	$226.50
Purchase #3	$180.98	8.332%	$196.0593	$196.06	$196.05	$196.10
Purchase #4	$132.60	11.520%	$147.8755	$147.88	$147.90	$147.90
Purchase #5	$117.92	4.364%	$123.066	$123.07	$123.05	$123.10
Purchase #6	$210.29	13.257%	$238.1681	$238.17	$238.15	$238.20
Purchase #7	$30.97	3.141%	$31.9428	$31.94	$31.95	$31.90
7 purchase totals =	$1,067.96		$1,156.9540	$1,156.96	$1,156.95	$1,157.10