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	$187.52	11.781%	$209.6117	$209.61	$209.60	$209.60
Purchase #2	$175.82	8.487%	$190.7418	$190.74	$190.75	$190.70
Purchase #3	$135.87	6.615%	$144.8578	$144.86	$144.85	$144.90
Purchase #4	$93.74	9.229%	$102.3913	$102.39	$102.40	$102.40
Purchase #5	$120.69	5.711%	$127.5826	$127.58	$127.60	$127.60
Purchase #6	$94.95	5.481%	$100.1542	$100.15	$100.15	$100.20
Purchase #7	$16.37	3.280%	$16.9069	$16.91	$16.90	$16.90
7 purchase totals =	$824.96		$892.2463	$892.24	$892.25	$892.30