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	$64.32	6.295%	$68.3689	$68.37	$68.35	$68.40
Purchase #2	$183.57	9.678%	$201.3359	$201.34	$201.35	$201.30
Purchase #3	$102.49	8.570%	$111.2734	$111.27	$111.25	$111.30
Purchase #4	$184.49	4.214%	$192.2644	$192.26	$192.25	$192.30
Purchase #5	$239.97	10.356%	$264.8213	$264.82	$264.80	$264.80
Purchase #6	$67.83	5.548%	$71.5932	$71.59	$71.60	$71.60
Purchase #7	$130.87	6.809%	$139.7809	$139.78	$139.80	$139.80
7 purchase totals =	$973.54		$1,049.4380	$1,049.43	$1,049.40	$1,049.50