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	$93.56	12.766%	$105.5039	$105.50	$105.50	$105.50
Purchase #2	$187.79	5.699%	$198.4922	$198.49	$198.50	$198.50
Purchase #3	$141.27	13.424%	$160.2341	$160.23	$160.25	$160.20
Purchase #4	$61.95	7.339%	$66.4965	$66.50	$66.50	$66.50
Purchase #5	$55.29	8.276%	$59.8658	$59.87	$59.85	$59.90
Purchase #6	$212.41	3.187%	$219.1795	$219.18	$219.20	$219.20
Purchase #7	$196.90	4.477%	$205.7152	$205.72	$205.70	$205.70
7 purchase totals =	$949.17		$1,015.4872	$1,015.49	$1,015.50	$1,015.50