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	$96.44	13.143%	$109.1151	$109.12	$109.10	$109.10
Purchase #2	$99.71	10.554%	$110.2334	$110.23	$110.25	$110.20
Purchase #3	$167.46	5.416%	$176.5296	$176.53	$176.55	$176.50
Purchase #4	$81.35	10.491%	$89.8844	$89.88	$89.90	$89.90
Purchase #5	$80.25	3.418%	$82.9929	$82.99	$83.00	$83.00
Purchase #6	$73.44	5.513%	$77.4887	$77.49	$77.50	$77.50
Purchase #7	$154.91	11.720%	$173.0655	$173.07	$173.05	$173.10
7 purchase totals =	$753.56		$819.3096	$819.31	$819.35	$819.30