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	$160.37	12.787%	$180.8765	$180.88	$180.90	$180.90
Purchase #2	$9.46	7.418%	$10.1617	$10.16	$10.15	$10.20
Purchase #3	$52.92	3.103%	$54.5621	$54.56	$54.55	$54.60
Purchase #4	$239.72	3.441%	$247.9688	$247.97	$247.95	$248.00
Purchase #5	$41.54	4.816%	$43.5406	$43.54	$43.55	$43.50
Purchase #6	$82.92	10.388%	$91.5337	$91.53	$91.55	$91.50
Purchase #7	$63.30	7.794%	$68.2336	$68.23	$68.25	$68.20
7 purchase totals =	$650.23		$696.8770	$696.87	$696.90	$696.90