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	$222.32	13.147%	$251.5484	$251.55	$251.55	$251.50
Purchase #2	$112.89	13.509%	$128.1403	$128.14	$128.15	$128.10
Purchase #3	$10.46	6.392%	$11.1286	$11.13	$11.15	$11.10
Purchase #4	$33.94	13.850%	$38.6407	$38.64	$38.65	$38.60
Purchase #5	$54.54	7.390%	$58.5705	$58.57	$58.55	$58.60
Purchase #6	$144.71	12.288%	$162.492	$162.49	$162.50	$162.50
Purchase #7	$169.69	3.484%	$175.602	$175.60	$175.60	$175.60
7 purchase totals =	$748.55		$826.1225	$826.12	$826.15	$826.00