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	$120.25	4.385%	$125.523	$125.52	$125.50	$125.50
Purchase #2	$168.68	4.536%	$176.3313	$176.33	$176.35	$176.30
Purchase #3	$120.66	5.623%	$127.4447	$127.44	$127.45	$127.40
Purchase #4	$110.54	9.386%	$120.9153	$120.92	$120.90	$120.90
Purchase #5	$104.90	6.211%	$111.4153	$111.42	$111.40	$111.40
Purchase #6	$155.87	8.173%	$168.6093	$168.61	$168.60	$168.60
Purchase #7	$19.59	11.698%	$21.8816	$21.88	$21.90	$21.90
7 purchase totals =	$800.49		$852.1205	$852.12	$852.10	$852.00