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	$131.60	10.181%	$144.9982	$145.00	$145.00	$145.00
Purchase #2	$186.96	12.419%	$210.1786	$210.18	$210.20	$210.20
Purchase #3	$29.55	13.278%	$33.4736	$33.47	$33.45	$33.50
Purchase #4	$228.96	11.849%	$256.0895	$256.09	$256.10	$256.10
Purchase #5	$239.61	6.233%	$254.5449	$254.54	$254.55	$254.50
Purchase #6	$89.60	10.115%	$98.663	$98.66	$98.65	$98.70
Purchase #7	$144.45	12.484%	$162.4831	$162.48	$162.50	$162.50
7 purchase totals =	$1,050.73		$1,160.4309	$1,160.42	$1,160.45	$1,160.50