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	$47.27	3.356%	$48.8564	$48.86	$48.85	$48.90
Purchase #2	$228.36	4.444%	$238.5083	$238.51	$238.50	$238.50
Purchase #3	$50.66	9.469%	$55.457	$55.46	$55.45	$55.50
Purchase #4	$156.75	5.324%	$165.0954	$165.10	$165.10	$165.10
Purchase #5	$50.91	12.801%	$57.427	$57.43	$57.45	$57.40
Purchase #6	$97.38	3.645%	$100.9295	$100.93	$100.95	$100.90
Purchase #7	$156.38	4.321%	$163.1372	$163.14	$163.15	$163.10
7 purchase totals =	$787.71		$829.4108	$829.43	$829.45	$829.40