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	$107.30	4.204%	$111.8109	$111.81	$111.80	$111.80
Purchase #2	$179.39	4.425%	$187.328	$187.33	$187.35	$187.30
Purchase #3	$69.82	13.763%	$79.4293	$79.43	$79.45	$79.40
Purchase #4	$122.84	3.509%	$127.1505	$127.15	$127.15	$127.20
Purchase #5	$34.31	7.549%	$36.9001	$36.90	$36.90	$36.90
Purchase #6	$20.39	4.679%	$21.344	$21.34	$21.35	$21.30
Purchase #7	$200.37	6.272%	$212.9372	$212.94	$212.95	$212.90
7 purchase totals =	$734.42		$776.9000	$776.90	$776.95	$776.80