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	$236.87	11.620%	$264.3943	$264.39	$264.40	$264.40
Purchase #2	$170.60	8.395%	$184.9219	$184.92	$184.90	$184.90
Purchase #3	$108.57	6.256%	$115.3621	$115.36	$115.35	$115.40
Purchase #4	$144.56	8.298%	$156.5556	$156.56	$156.55	$156.60
Purchase #5	$61.56	7.197%	$65.9905	$65.99	$66.00	$66.00
Purchase #6	$193.38	3.561%	$200.2663	$200.27	$200.25	$200.30
Purchase #7	$53.64	3.443%	$55.4868	$55.49	$55.50	$55.50
7 purchase totals =	$969.18		$1,042.9775	$1,042.98	$1,042.95	$1,043.10