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	$37.39	3.102%	$38.5498	$38.55	$38.55	$38.50
Purchase #2	$144.82	12.866%	$163.4525	$163.45	$163.45	$163.50
Purchase #3	$52.88	4.790%	$55.413	$55.41	$55.40	$55.40
Purchase #4	$219.56	3.179%	$226.5398	$226.54	$226.55	$226.50
Purchase #5	$173.25	12.360%	$194.6637	$194.66	$194.65	$194.70
Purchase #6	$212.91	9.649%	$233.4537	$233.45	$233.45	$233.50
Purchase #7	$240.66	6.650%	$256.6639	$256.66	$256.65	$256.70
7 purchase totals =	$1,081.47		$1,168.7364	$1,168.72	$1,168.70	$1,168.80