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	$170.33	13.227%	$192.8595	$192.86	$192.85	$192.90
Purchase #2	$24.97	3.204%	$25.77	$25.77	$25.75	$25.80
Purchase #3	$96.71	9.699%	$106.0899	$106.09	$106.10	$106.10
Purchase #4	$17.52	3.164%	$18.0743	$18.07	$18.05	$18.10
Purchase #5	$151.61	7.205%	$162.5335	$162.53	$162.55	$162.50
Purchase #6	$92.73	8.115%	$100.255	$100.26	$100.25	$100.30
Purchase #7	$29.52	7.822%	$31.8291	$31.83	$31.85	$31.80
7 purchase totals =	$583.39		$637.4113	$637.41	$637.40	$637.50