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	$141.88	5.771%	$150.0679	$150.07	$150.05	$150.10
Purchase #2	$196.39	3.315%	$202.9003	$202.90	$202.90	$202.90
Purchase #3	$107.25	4.754%	$112.3487	$112.35	$112.35	$112.30
Purchase #4	$50.96	3.744%	$52.8679	$52.87	$52.85	$52.90
Purchase #5	$214.40	11.557%	$239.1782	$239.18	$239.20	$239.20
Purchase #6	$83.83	6.514%	$89.2907	$89.29	$89.30	$89.30
Purchase #7	$237.92	10.357%	$262.5614	$262.56	$262.55	$262.60
7 purchase totals =	$1,032.63		$1,109.2151	$1,109.22	$1,109.20	$1,109.30