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	$155.30	3.633%	$160.942	$160.94	$160.95	$160.90
Purchase #2	$222.29	9.131%	$242.5873	$242.59	$242.60	$242.60
Purchase #3	$89.25	11.577%	$99.5825	$99.58	$99.60	$99.60
Purchase #4	$238.92	8.237%	$258.5998	$258.60	$258.60	$258.60
Purchase #5	$168.32	11.528%	$187.7239	$187.72	$187.70	$187.70
Purchase #6	$96.49	7.669%	$103.8898	$103.89	$103.90	$103.90
Purchase #7	$113.84	12.603%	$128.1873	$128.19	$128.20	$128.20
7 purchase totals =	$1,084.41		$1,181.5126	$1,181.51	$1,181.55	$1,181.50