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	$95.68	6.176%	$101.5892	$101.59	$101.60	$101.60
Purchase #2	$42.89	10.786%	$47.5161	$47.52	$47.50	$47.50
Purchase #3	$195.52	11.692%	$218.3802	$218.38	$218.40	$218.40
Purchase #4	$210.44	3.681%	$218.1863	$218.19	$218.20	$218.20
Purchase #5	$32.63	7.712%	$35.1464	$35.15	$35.15	$35.10
Purchase #6	$41.34	13.218%	$46.8043	$46.80	$46.80	$46.80
Purchase #7	$133.56	13.689%	$151.843	$151.84	$151.85	$151.80
7 purchase totals =	$752.06		$819.4655	$819.47	$819.50	$819.40