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	$10.77	3.603%	$11.158	$11.16	$11.15	$11.20
Purchase #2	$162.86	10.699%	$180.2844	$180.28	$180.30	$180.30
Purchase #3	$184.32	9.369%	$201.5889	$201.59	$201.60	$201.60
Purchase #4	$232.89	12.809%	$262.7209	$262.72	$262.70	$262.70
Purchase #5	$59.42	8.132%	$64.252	$64.25	$64.25	$64.30
Purchase #6	$215.79	8.227%	$233.543	$233.54	$233.55	$233.50
Purchase #7	$133.52	12.580%	$150.3168	$150.32	$150.30	$150.30
7 purchase totals =	$999.57		$1,103.8640	$1,103.86	$1,103.85	$1,103.90