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	$103.42	7.605%	$111.2851	$111.29	$111.30	$111.30
Purchase #2	$78.80	5.434%	$83.082	$83.08	$83.10	$83.10
Purchase #3	$87.87	13.439%	$99.6788	$99.68	$99.70	$99.70
Purchase #4	$122.66	4.558%	$128.2508	$128.25	$128.25	$128.30
Purchase #5	$228.42	5.527%	$241.0448	$241.04	$241.05	$241.00
Purchase #6	$196.73	11.387%	$219.1316	$219.13	$219.15	$219.10
Purchase #7	$162.98	11.266%	$181.3413	$181.34	$181.35	$181.30
7 purchase totals =	$980.88		$1,063.8144	$1,063.81	$1,063.90	$1,063.80