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	$118.32	4.269%	$123.3711	$123.37	$123.35	$123.40
Purchase #2	$10.57	10.712%	$11.7023	$11.70	$11.70	$11.70
Purchase #3	$112.74	13.395%	$127.8415	$127.84	$127.85	$127.80
Purchase #4	$51.30	5.151%	$53.9425	$53.94	$53.95	$53.90
Purchase #5	$127.77	5.235%	$134.4588	$134.46	$134.45	$134.50
Purchase #6	$28.54	5.494%	$30.108	$30.11	$30.10	$30.10
Purchase #7	$86.55	4.426%	$90.3807	$90.38	$90.40	$90.40
7 purchase totals =	$535.79		$571.8049	$571.80	$571.80	$571.80