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	$179.89	9.476%	$196.9364	$196.94	$196.95	$196.90
Purchase #2	$219.54	3.432%	$227.0746	$227.07	$227.05	$227.10
Purchase #3	$107.81	10.662%	$119.3047	$119.30	$119.30	$119.30
Purchase #4	$31.74	3.424%	$32.8268	$32.83	$32.85	$32.80
Purchase #5	$91.46	8.418%	$99.1591	$99.16	$99.15	$99.20
Purchase #6	$176.35	3.403%	$182.3512	$182.35	$182.35	$182.40
Purchase #7	$163.35	11.295%	$181.8004	$181.80	$181.80	$181.80
7 purchase totals =	$970.14		$1,039.4532	$1,039.45	$1,039.45	$1,039.50