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	$173.83	9.868%	$190.9835	$190.98	$191.00	$191.00
Purchase #2	$197.28	5.501%	$208.1324	$208.13	$208.15	$208.10
Purchase #3	$9.82	5.288%	$10.3393	$10.34	$10.35	$10.30
Purchase #4	$208.37	8.499%	$226.0794	$226.08	$226.10	$226.10
Purchase #5	$116.32	5.761%	$123.0212	$123.02	$123.00	$123.00
Purchase #6	$113.47	12.518%	$127.6742	$127.67	$127.65	$127.70
Purchase #7	$173.80	11.518%	$193.8183	$193.82	$193.80	$193.80
7 purchase totals =	$992.89		$1,080.0483	$1,080.04	$1,080.05	$1,080.00