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	$166.69	4.148%	$173.6043	$173.60	$173.60	$173.60
Purchase #2	$10.72	6.807%	$11.4497	$11.45	$11.45	$11.40
Purchase #3	$165.98	5.597%	$175.2699	$175.27	$175.25	$175.30
Purchase #4	$86.71	4.105%	$90.2694	$90.27	$90.25	$90.30
Purchase #5	$89.59	13.601%	$101.7751	$101.78	$101.80	$101.80
Purchase #6	$38.61	7.163%	$41.3756	$41.38	$41.40	$41.40
Purchase #7	$15.56	11.158%	$17.2962	$17.30	$17.30	$17.30
7 purchase totals =	$573.86		$611.0402	$611.05	$611.05	$611.10