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	$129.91	8.762%	$141.2927	$141.29	$141.30	$141.30
Purchase #2	$94.72	5.327%	$99.7657	$99.77	$99.75	$99.80
Purchase #3	$28.38	11.856%	$31.7447	$31.74	$31.75	$31.70
Purchase #4	$16.63	6.477%	$17.7071	$17.71	$17.70	$17.70
Purchase #5	$37.79	5.531%	$39.8802	$39.88	$39.90	$39.90
Purchase #6	$230.56	6.600%	$245.777	$245.78	$245.80	$245.80
Purchase #7	$104.92	6.124%	$111.3453	$111.35	$111.35	$111.30
7 purchase totals =	$642.91		$687.5127	$687.52	$687.55	$687.50