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	$153.63	9.718%	$168.5598	$168.56	$168.55	$168.60
Purchase #2	$218.86	13.276%	$247.9159	$247.92	$247.90	$247.90
Purchase #3	$74.39	6.555%	$79.2663	$79.27	$79.25	$79.30
Purchase #4	$163.61	11.172%	$181.8885	$181.89	$181.90	$181.90
Purchase #5	$25.84	10.504%	$28.5542	$28.55	$28.55	$28.60
Purchase #6	$153.43	10.458%	$169.4757	$169.48	$169.50	$169.50
Purchase #7	$161.31	13.743%	$183.4788	$183.48	$183.50	$183.50
7 purchase totals =	$951.07		$1,059.1392	$1,059.15	$1,059.15	$1,059.30