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	$68.93	3.703%	$71.4825	$71.48	$71.50	$71.50
Purchase #2	$30.92	3.502%	$32.0028	$32.00	$32.00	$32.00
Purchase #3	$243.52	11.245%	$270.9038	$270.90	$270.90	$270.90
Purchase #4	$196.85	6.377%	$209.4031	$209.40	$209.40	$209.40
Purchase #5	$151.49	10.289%	$167.0768	$167.08	$167.10	$167.10
Purchase #6	$116.82	13.367%	$132.4353	$132.44	$132.45	$132.40
Purchase #7	$185.32	6.445%	$197.2639	$197.26	$197.25	$197.30
7 purchase totals =	$993.85		$1,080.5682	$1,080.56	$1,080.60	$1,080.60