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	$150.55	3.806%	$156.2799	$156.28	$156.30	$156.30
Purchase #2	$16.89	11.677%	$18.8622	$18.86	$18.85	$18.90
Purchase #3	$155.37	10.558%	$171.774	$171.77	$171.75	$171.80
Purchase #4	$73.41	6.779%	$78.3865	$78.39	$78.40	$78.40
Purchase #5	$60.64	5.691%	$64.091	$64.09	$64.10	$64.10
Purchase #6	$145.79	13.392%	$165.3142	$165.31	$165.30	$165.30
Purchase #7	$127.61	9.332%	$139.5186	$139.52	$139.50	$139.50
7 purchase totals =	$730.26		$794.2264	$794.22	$794.20	$794.30