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	$57.47	13.593%	$65.2819	$65.28	$65.30	$65.30
Purchase #2	$150.56	6.147%	$159.8149	$159.81	$159.80	$159.80
Purchase #3	$206.67	4.487%	$215.9433	$215.94	$215.95	$215.90
Purchase #4	$242.72	3.264%	$250.6424	$250.64	$250.65	$250.60
Purchase #5	$222.41	5.617%	$234.9028	$234.90	$234.90	$234.90
Purchase #6	$194.72	7.211%	$208.7613	$208.76	$208.75	$208.80
Purchase #7	$234.25	4.721%	$245.3089	$245.31	$245.30	$245.30
7 purchase totals =	$1,308.80		$1,380.6555	$1,380.64	$1,380.65	$1,380.60