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	$107.49	4.102%	$111.8992	$111.90	$111.90	$111.90
Purchase #2	$205.94	3.222%	$212.5754	$212.58	$212.60	$212.60
Purchase #3	$250.41	11.838%	$280.0535	$280.05	$280.05	$280.10
Purchase #4	$39.31	3.604%	$40.7267	$40.73	$40.75	$40.70
Purchase #5	$219.29	12.631%	$246.9885	$246.99	$247.00	$247.00
Purchase #6	$61.98	8.714%	$67.3809	$67.38	$67.40	$67.40
Purchase #7	$82.87	3.646%	$85.8914	$85.89	$85.90	$85.90
7 purchase totals =	$967.29		$1,045.5156	$1,045.52	$1,045.60	$1,045.60