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	$145.52	13.208%	$164.7403	$164.74	$164.75	$164.70
Purchase #2	$131.70	7.179%	$141.1547	$141.15	$141.15	$141.20
Purchase #3	$157.66	6.293%	$167.5815	$167.58	$167.60	$167.60
Purchase #4	$76.38	12.773%	$86.136	$86.14	$86.15	$86.10
Purchase #5	$212.56	9.514%	$232.783	$232.78	$232.80	$232.80
Purchase #6	$20.62	4.388%	$21.5248	$21.52	$21.50	$21.50
Purchase #7	$56.47	5.844%	$59.7701	$59.77	$59.75	$59.80
7 purchase totals =	$800.91		$873.6904	$873.68	$873.70	$873.70