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	$159.39	12.452%	$179.2372	$179.24	$179.25	$179.20
Purchase #2	$6.68	11.127%	$7.4233	$7.42	$7.40	$7.40
Purchase #3	$62.83	4.711%	$65.7899	$65.79	$65.80	$65.80
Purchase #4	$39.80	6.551%	$42.4073	$42.41	$42.40	$42.40
Purchase #5	$19.75	7.837%	$21.2978	$21.30	$21.30	$21.30
Purchase #6	$65.90	7.111%	$70.5861	$70.59	$70.60	$70.60
Purchase #7	$9.94	8.322%	$10.7672	$10.77	$10.75	$10.80
7 purchase totals =	$364.29		$397.5088	$397.52	$397.50	$397.50