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	$168.55	3.325%	$174.1543	$174.15	$174.15	$174.20
Purchase #2	$101.87	9.144%	$111.185	$111.19	$111.20	$111.20
Purchase #3	$100.75	10.400%	$111.228	$111.23	$111.25	$111.20
Purchase #4	$144.43	12.387%	$162.3205	$162.32	$162.30	$162.30
Purchase #5	$25.81	5.482%	$27.2249	$27.22	$27.20	$27.20
Purchase #6	$105.32	7.105%	$112.803	$112.80	$112.80	$112.80
Purchase #7	$32.99	7.170%	$35.3554	$35.36	$35.35	$35.40
7 purchase totals =	$679.72		$734.2711	$734.27	$734.25	$734.30