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	$95.36	12.342%	$107.1293	$107.13	$107.15	$107.10
Purchase #2	$77.31	11.604%	$86.2811	$86.28	$86.30	$86.30
Purchase #3	$49.76	4.115%	$51.8076	$51.81	$51.80	$51.80
Purchase #4	$48.57	10.103%	$53.477	$53.48	$53.50	$53.50
Purchase #5	$15.69	4.853%	$16.4514	$16.45	$16.45	$16.50
Purchase #6	$76.52	8.849%	$83.2913	$83.29	$83.30	$83.30
Purchase #7	$55.50	11.214%	$61.7238	$61.72	$61.70	$61.70
7 purchase totals =	$418.71		$460.1615	$460.16	$460.20	$460.20