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	$224.41	7.251%	$240.682	$240.68	$240.70	$240.70
Purchase #2	$119.55	13.111%	$135.2242	$135.22	$135.20	$135.20
Purchase #3	$70.44	11.649%	$78.6456	$78.65	$78.65	$78.60
Purchase #4	$171.47	13.319%	$194.3081	$194.31	$194.30	$194.30
Purchase #5	$118.57	8.380%	$128.5062	$128.51	$128.50	$128.50
Purchase #6	$41.42	5.186%	$43.568	$43.57	$43.55	$43.60
Purchase #7	$175.30	5.724%	$185.3342	$185.33	$185.35	$185.30
7 purchase totals =	$921.16		$1,006.2683	$1,006.27	$1,006.25	$1,006.20