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	$150.30	5.188%	$158.0976	$158.10	$158.10	$158.10
Purchase #2	$86.78	5.293%	$91.3733	$91.37	$91.35	$91.40
Purchase #3	$75.37	4.584%	$78.825	$78.83	$78.85	$78.80
Purchase #4	$103.29	11.394%	$115.0589	$115.06	$115.05	$115.10
Purchase #5	$119.25	5.141%	$125.3806	$125.38	$125.40	$125.40
Purchase #6	$122.71	3.742%	$127.3018	$127.30	$127.30	$127.30
Purchase #7	$31.31	5.170%	$32.9287	$32.93	$32.95	$32.90
7 purchase totals =	$689.01		$728.9659	$728.97	$729.00	$729.00