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	$144.83	13.659%	$164.6123	$164.61	$164.60	$164.60
Purchase #2	$124.45	12.368%	$139.842	$139.84	$139.85	$139.80
Purchase #3	$142.97	7.571%	$153.7943	$153.79	$153.80	$153.80
Purchase #4	$132.73	5.194%	$139.624	$139.62	$139.60	$139.60
Purchase #5	$23.85	6.686%	$25.4446	$25.44	$25.45	$25.40
Purchase #6	$250.37	10.161%	$275.8101	$275.81	$275.80	$275.80
Purchase #7	$247.69	6.165%	$262.9601	$262.96	$262.95	$263.00
7 purchase totals =	$1,066.89		$1,162.0874	$1,162.07	$1,162.05	$1,162.00