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	$233.79	9.228%	$255.3641	$255.36	$255.35	$255.40
Purchase #2	$212.32	8.396%	$230.1464	$230.15	$230.15	$230.10
Purchase #3	$129.83	4.620%	$135.8281	$135.83	$135.85	$135.80
Purchase #4	$79.94	13.358%	$90.6184	$90.62	$90.60	$90.60
Purchase #5	$30.77	10.287%	$33.9353	$33.94	$33.95	$33.90
Purchase #6	$220.81	12.266%	$247.8946	$247.89	$247.90	$247.90
Purchase #7	$41.70	3.673%	$43.2316	$43.23	$43.25	$43.20
7 purchase totals =	$949.16		$1,037.0185	$1,037.02	$1,037.05	$1,036.90