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	$188.99	8.819%	$205.657	$205.66	$205.65	$205.70
Purchase #2	$116.33	10.695%	$128.7715	$128.77	$128.75	$128.80
Purchase #3	$135.56	11.292%	$150.8674	$150.87	$150.85	$150.90
Purchase #4	$213.28	6.303%	$226.723	$226.72	$226.70	$226.70
Purchase #5	$229.90	8.423%	$249.2645	$249.26	$249.25	$249.30
Purchase #6	$29.32	12.480%	$32.9791	$32.98	$33.00	$33.00
Purchase #7	$61.77	8.606%	$67.0859	$67.09	$67.10	$67.10
7 purchase totals =	$975.15		$1,061.3484	$1,061.35	$1,061.30	$1,061.50