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	$48.74	11.718%	$54.4514	$54.45	$54.45	$54.50
Purchase #2	$67.98	13.119%	$76.8983	$76.90	$76.90	$76.90
Purchase #3	$183.39	6.800%	$195.8605	$195.86	$195.85	$195.90
Purchase #4	$197.62	12.547%	$222.4154	$222.42	$222.40	$222.40
Purchase #5	$205.54	4.304%	$214.3864	$214.39	$214.40	$214.40
Purchase #6	$250.51	5.461%	$264.1904	$264.19	$264.20	$264.20
Purchase #7	$52.79	9.340%	$57.7206	$57.72	$57.70	$57.70
7 purchase totals =	$1,006.57		$1,085.9230	$1,085.93	$1,085.90	$1,086.00