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	$126.88	13.512%	$144.024	$144.02	$144.00	$144.00
Purchase #2	$80.49	7.534%	$86.5541	$86.55	$86.55	$86.60
Purchase #3	$181.89	6.812%	$194.2803	$194.28	$194.30	$194.30
Purchase #4	$150.50	4.226%	$156.8601	$156.86	$156.85	$156.90
Purchase #5	$132.67	3.220%	$136.942	$136.94	$136.95	$136.90
Purchase #6	$198.88	11.568%	$221.8864	$221.89	$221.90	$221.90
Purchase #7	$18.51	10.312%	$20.4188	$20.42	$20.40	$20.40
7 purchase totals =	$889.82		$960.9657	$960.96	$960.95	$961.00