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	$178.47	3.488%	$184.695	$184.70	$184.70	$184.70
Purchase #2	$103.81	7.854%	$111.9632	$111.96	$111.95	$112.00
Purchase #3	$225.63	8.634%	$245.1109	$245.11	$245.10	$245.10
Purchase #4	$151.76	8.686%	$164.9419	$164.94	$164.95	$164.90
Purchase #5	$110.96	5.267%	$116.8043	$116.80	$116.80	$116.80
Purchase #6	$108.37	7.397%	$116.3861	$116.39	$116.40	$116.40
Purchase #7	$101.51	10.803%	$112.4761	$112.48	$112.50	$112.50
7 purchase totals =	$980.51		$1,052.3775	$1,052.38	$1,052.40	$1,052.40