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	$151.97	7.162%	$162.8541	$162.85	$162.85	$162.90
Purchase #2	$47.45	9.682%	$52.0441	$52.04	$52.05	$52.00
Purchase #3	$233.77	13.704%	$265.8058	$265.81	$265.80	$265.80
Purchase #4	$191.88	8.775%	$208.7175	$208.72	$208.70	$208.70
Purchase #5	$198.99	8.307%	$215.5201	$215.52	$215.50	$215.50
Purchase #6	$186.69	4.749%	$195.5559	$195.56	$195.55	$195.60
Purchase #7	$42.31	8.277%	$45.812	$45.81	$45.80	$45.80
7 purchase totals =	$1,053.06		$1,146.3095	$1,146.31	$1,146.25	$1,146.30