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	$41.27	9.414%	$45.1552	$45.16	$45.15	$45.20
Purchase #2	$103.69	11.409%	$115.52	$115.52	$115.50	$115.50
Purchase #3	$111.31	3.113%	$114.7751	$114.78	$114.80	$114.80
Purchase #4	$35.44	9.343%	$38.7512	$38.75	$38.75	$38.80
Purchase #5	$228.52	5.698%	$241.5411	$241.54	$241.55	$241.50
Purchase #6	$12.55	6.773%	$13.4	$13.40	$13.40	$13.40
Purchase #7	$40.74	6.132%	$43.2382	$43.24	$43.25	$43.20
7 purchase totals =	$573.52		$612.3808	$612.39	$612.40	$612.40