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	$129.83	12.393%	$145.9198	$145.92	$145.90	$145.90
Purchase #2	$64.50	11.295%	$71.7853	$71.79	$71.80	$71.80
Purchase #3	$227.29	10.700%	$251.61	$251.61	$251.60	$251.60
Purchase #4	$219.81	5.720%	$232.3831	$232.38	$232.40	$232.40
Purchase #5	$182.54	4.166%	$190.1446	$190.14	$190.15	$190.10
Purchase #6	$51.95	5.339%	$54.7236	$54.72	$54.70	$54.70
Purchase #7	$99.70	13.419%	$113.0787	$113.08	$113.10	$113.10
7 purchase totals =	$975.62		$1,059.6451	$1,059.64	$1,059.65	$1,059.60