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	$167.33	10.496%	$184.893	$184.89	$184.90	$184.90
Purchase #2	$150.38	3.249%	$155.2658	$155.27	$155.25	$155.30
Purchase #3	$63.87	6.410%	$67.9641	$67.96	$67.95	$68.00
Purchase #4	$193.59	13.593%	$219.9047	$219.90	$219.90	$219.90
Purchase #5	$74.82	3.144%	$77.1723	$77.17	$77.15	$77.20
Purchase #6	$176.89	12.390%	$198.8067	$198.81	$198.80	$198.80
Purchase #7	$164.67	4.773%	$172.5297	$172.53	$172.55	$172.50
7 purchase totals =	$991.55		$1,076.5363	$1,076.53	$1,076.50	$1,076.60