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	$100.42	13.865%	$114.3432	$114.34	$114.35	$114.30
Purchase #2	$145.32	9.193%	$158.6793	$158.68	$158.70	$158.70
Purchase #3	$122.81	3.510%	$127.1206	$127.12	$127.10	$127.10
Purchase #4	$60.44	11.611%	$67.4577	$67.46	$67.45	$67.50
Purchase #5	$42.39	3.297%	$43.7876	$43.79	$43.80	$43.80
Purchase #6	$48.89	9.135%	$53.3561	$53.36	$53.35	$53.40
Purchase #7	$201.32	8.487%	$218.406	$218.41	$218.40	$218.40
7 purchase totals =	$721.59		$783.1505	$783.16	$783.15	$783.20