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	$141.26	7.156%	$151.3686	$151.37	$151.35	$151.40
Purchase #2	$101.93	6.796%	$108.8572	$108.86	$108.85	$108.90
Purchase #3	$174.89	7.665%	$188.2953	$188.30	$188.30	$188.30
Purchase #4	$110.58	3.635%	$114.5996	$114.60	$114.60	$114.60
Purchase #5	$72.62	7.299%	$77.9205	$77.92	$77.90	$77.90
Purchase #6	$41.59	12.564%	$46.8154	$46.82	$46.80	$46.80
Purchase #7	$208.75	3.262%	$215.5594	$215.56	$215.55	$215.60
7 purchase totals =	$851.62		$903.4160	$903.43	$903.35	$903.50