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	$107.84	9.721%	$118.3231	$118.32	$118.30	$118.30
Purchase #2	$189.37	3.795%	$196.5566	$196.56	$196.55	$196.60
Purchase #3	$34.64	9.590%	$37.962	$37.96	$37.95	$38.00
Purchase #4	$249.38	8.605%	$270.8391	$270.84	$270.85	$270.80
Purchase #5	$136.76	4.719%	$143.2137	$143.21	$143.20	$143.20
Purchase #6	$96.39	9.459%	$105.5075	$105.51	$105.50	$105.50
Purchase #7	$233.50	13.154%	$264.2146	$264.21	$264.20	$264.20
7 purchase totals =	$1,047.88		$1,136.6166	$1,136.61	$1,136.55	$1,136.60