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	$89.34	3.500%	$92.4669	$92.47	$92.45	$92.50
Purchase #2	$18.34	7.524%	$19.7199	$19.72	$19.70	$19.70
Purchase #3	$89.80	10.321%	$99.0683	$99.07	$99.05	$99.10
Purchase #4	$19.86	6.194%	$21.0901	$21.09	$21.10	$21.10
Purchase #5	$18.58	7.107%	$19.9005	$19.90	$19.90	$19.90
Purchase #6	$131.86	7.719%	$142.0383	$142.04	$142.05	$142.00
Purchase #7	$29.65	8.129%	$32.0602	$32.06	$32.05	$32.10
7 purchase totals =	$397.43		$426.3442	$426.35	$426.30	$426.40