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	$97.76	11.275%	$108.7824	$108.78	$108.80	$108.80
Purchase #2	$13.37	4.144%	$13.9241	$13.92	$13.90	$13.90
Purchase #3	$209.60	7.759%	$225.8629	$225.86	$225.85	$225.90
Purchase #4	$112.29	5.583%	$118.5592	$118.56	$118.55	$118.60
Purchase #5	$133.83	4.303%	$139.5887	$139.59	$139.60	$139.60
Purchase #6	$244.55	7.744%	$263.488	$263.49	$263.50	$263.50
Purchase #7	$145.50	9.263%	$158.9777	$158.98	$159.00	$159.00
7 purchase totals =	$956.90		$1,029.1830	$1,029.18	$1,029.20	$1,029.30