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	$141.66	11.131%	$157.4282	$157.43	$157.45	$157.40
Purchase #2	$108.28	5.550%	$114.2895	$114.29	$114.30	$114.30
Purchase #3	$185.92	5.485%	$196.1177	$196.12	$196.10	$196.10
Purchase #4	$175.49	13.309%	$198.846	$198.85	$198.85	$198.80
Purchase #5	$18.97	13.314%	$21.4957	$21.50	$21.50	$21.50
Purchase #6	$171.48	9.580%	$187.9078	$187.91	$187.90	$187.90
Purchase #7	$248.79	5.439%	$262.3217	$262.32	$262.30	$262.30
7 purchase totals =	$1,050.59		$1,138.4066	$1,138.42	$1,138.40	$1,138.30