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	$153.89	6.855%	$164.4392	$164.44	$164.45	$164.40
Purchase #2	$167.50	11.719%	$187.1293	$187.13	$187.15	$187.10
Purchase #3	$168.25	9.514%	$184.2573	$184.26	$184.25	$184.30
Purchase #4	$205.60	7.747%	$221.5278	$221.53	$221.55	$221.50
Purchase #5	$34.93	4.192%	$36.3943	$36.39	$36.40	$36.40
Purchase #6	$90.86	13.692%	$103.3006	$103.30	$103.30	$103.30
Purchase #7	$250.61	5.700%	$264.8948	$264.89	$264.90	$264.90
7 purchase totals =	$1,071.64		$1,161.9433	$1,161.94	$1,162.00	$1,161.90