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	$95.38	5.505%	$100.6307	$100.63	$100.65	$100.60
Purchase #2	$29.32	13.281%	$33.214	$33.21	$33.20	$33.20
Purchase #3	$197.68	10.285%	$218.0114	$218.01	$218.00	$218.00
Purchase #4	$152.83	10.569%	$168.9826	$168.98	$169.00	$169.00
Purchase #5	$33.30	5.411%	$35.1019	$35.10	$35.10	$35.10
Purchase #6	$231.95	13.178%	$262.5164	$262.52	$262.50	$262.50
Purchase #7	$248.45	5.826%	$262.9247	$262.92	$262.90	$262.90
7 purchase totals =	$988.91		$1,081.3817	$1,081.37	$1,081.35	$1,081.30