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	$191.94	7.122%	$205.61	$205.61	$205.60	$205.60
Purchase #2	$138.81	4.425%	$144.9523	$144.95	$144.95	$145.00
Purchase #3	$55.41	8.844%	$60.3105	$60.31	$60.30	$60.30
Purchase #4	$79.37	13.298%	$89.9246	$89.92	$89.90	$89.90
Purchase #5	$66.61	6.107%	$70.6779	$70.68	$70.70	$70.70
Purchase #6	$72.84	5.470%	$76.8243	$76.82	$76.80	$76.80
Purchase #7	$140.65	7.163%	$150.7248	$150.72	$150.70	$150.70
7 purchase totals =	$745.63		$799.0244	$799.01	$798.95	$799.00