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	$91.94	13.719%	$104.5532	$104.55	$104.55	$104.60
Purchase #2	$83.66	7.319%	$89.7831	$89.78	$89.80	$89.80
Purchase #3	$33.70	6.841%	$36.0054	$36.01	$36.00	$36.00
Purchase #4	$9.59	10.768%	$10.6227	$10.62	$10.60	$10.60
Purchase #5	$17.61	7.632%	$18.954	$18.95	$18.95	$19.00
Purchase #6	$201.59	6.573%	$214.8405	$214.84	$214.85	$214.80
Purchase #7	$38.80	3.251%	$40.0614	$40.06	$40.05	$40.10
7 purchase totals =	$476.89		$514.8203	$514.81	$514.80	$514.90