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	$113.43	12.243%	$127.3172	$127.32	$127.30	$127.30
Purchase #2	$111.37	3.813%	$115.6165	$115.62	$115.60	$115.60
Purchase #3	$5.97	9.272%	$6.5235	$6.52	$6.50	$6.50
Purchase #4	$19.64	3.347%	$20.2974	$20.30	$20.30	$20.30
Purchase #5	$48.82	4.123%	$50.8328	$50.83	$50.85	$50.80
Purchase #6	$6.47	6.846%	$6.9129	$6.91	$6.90	$6.90
Purchase #7	$35.74	6.126%	$37.9294	$37.93	$37.95	$37.90
7 purchase totals =	$341.44		$365.4297	$365.43	$365.40	$365.30