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	$22.89	4.190%	$23.8491	$23.85	$23.85	$23.80
Purchase #2	$89.88	6.105%	$95.3672	$95.37	$95.35	$95.40
Purchase #3	$60.43	3.118%	$62.3142	$62.31	$62.30	$62.30
Purchase #4	$221.28	7.677%	$238.2677	$238.27	$238.25	$238.30
Purchase #5	$185.39	3.768%	$192.3755	$192.38	$192.40	$192.40
Purchase #6	$45.78	4.314%	$47.7549	$47.75	$47.75	$47.80
Purchase #7	$81.81	9.583%	$89.6499	$89.65	$89.65	$89.60
7 purchase totals =	$707.46		$749.5785	$749.58	$749.55	$749.60