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	$140.62	3.781%	$145.9368	$145.94	$145.95	$145.90
Purchase #2	$110.68	7.300%	$118.7596	$118.76	$118.75	$118.80
Purchase #3	$86.85	3.666%	$90.0339	$90.03	$90.05	$90.00
Purchase #4	$239.64	11.764%	$267.8312	$267.83	$267.85	$267.80
Purchase #5	$156.95	5.655%	$165.8255	$165.83	$165.85	$165.80
Purchase #6	$29.93	4.350%	$31.232	$31.23	$31.25	$31.20
Purchase #7	$240.28	9.161%	$262.2921	$262.29	$262.30	$262.30
7 purchase totals =	$1,004.95		$1,081.9111	$1,081.91	$1,082.00	$1,081.80