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	$239.51	9.494%	$262.2491	$262.25	$262.25	$262.20
Purchase #2	$45.27	13.870%	$51.5489	$51.55	$51.55	$51.50
Purchase #3	$184.45	8.674%	$200.4492	$200.45	$200.45	$200.40
Purchase #4	$38.56	5.131%	$40.5385	$40.54	$40.55	$40.50
Purchase #5	$216.53	10.760%	$239.8286	$239.83	$239.85	$239.80
Purchase #6	$48.81	12.153%	$54.7419	$54.74	$54.75	$54.70
Purchase #7	$198.54	13.280%	$224.9061	$224.91	$224.90	$224.90
7 purchase totals =	$971.67		$1,074.2623	$1,074.27	$1,074.30	$1,074.00