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	$97.83	7.390%	$105.0596	$105.06	$105.05	$105.10
Purchase #2	$79.35	12.299%	$89.1093	$89.11	$89.10	$89.10
Purchase #3	$69.50	4.272%	$72.469	$72.47	$72.45	$72.50
Purchase #4	$18.59	13.215%	$21.0467	$21.05	$21.05	$21.00
Purchase #5	$177.62	3.324%	$183.5241	$183.52	$183.50	$183.50
Purchase #6	$222.94	13.837%	$253.7882	$253.79	$253.80	$253.80
Purchase #7	$170.52	10.361%	$188.1876	$188.19	$188.20	$188.20
7 purchase totals =	$836.35		$913.1845	$913.19	$913.15	$913.20