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	$5.41	9.754%	$5.9377	$5.94	$5.95	$5.90
Purchase #2	$132.45	3.396%	$136.948	$136.95	$136.95	$136.90
Purchase #3	$155.39	3.174%	$160.3221	$160.32	$160.30	$160.30
Purchase #4	$144.63	12.329%	$162.4614	$162.46	$162.45	$162.50
Purchase #5	$241.98	3.514%	$250.4832	$250.48	$250.50	$250.50
Purchase #6	$206.58	7.693%	$222.4722	$222.47	$222.45	$222.50
Purchase #7	$200.98	7.806%	$216.6685	$216.67	$216.65	$216.70
7 purchase totals =	$1,087.42		$1,155.2931	$1,155.29	$1,155.25	$1,155.30