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	$152.98	9.461%	$167.4534	$167.45	$167.45	$167.50
Purchase #2	$76.56	7.103%	$81.9981	$82.00	$82.00	$82.00
Purchase #3	$141.32	12.258%	$158.643	$158.64	$158.65	$158.60
Purchase #4	$33.30	9.525%	$36.4718	$36.47	$36.45	$36.50
Purchase #5	$188.50	11.578%	$210.3245	$210.32	$210.30	$210.30
Purchase #6	$40.51	9.342%	$44.2944	$44.29	$44.30	$44.30
Purchase #7	$135.76	12.305%	$152.4653	$152.47	$152.45	$152.50
7 purchase totals =	$768.93		$851.6505	$851.64	$851.60	$851.70