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	$173.60	6.506%	$184.8944	$184.89	$184.90	$184.90
Purchase #2	$111.94	5.674%	$118.2915	$118.29	$118.30	$118.30
Purchase #3	$184.52	3.555%	$191.0797	$191.08	$191.10	$191.10
Purchase #4	$155.56	6.335%	$165.4147	$165.41	$165.40	$165.40
Purchase #5	$118.73	7.665%	$127.8307	$127.83	$127.85	$127.80
Purchase #6	$226.73	5.163%	$238.4361	$238.44	$238.45	$238.40
Purchase #7	$111.99	6.296%	$119.0409	$119.04	$119.05	$119.00
7 purchase totals =	$1,083.07		$1,144.9880	$1,144.98	$1,145.05	$1,144.90