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	$181.45	6.489%	$193.2243	$193.22	$193.20	$193.20
Purchase #2	$100.38	11.163%	$111.5854	$111.59	$111.60	$111.60
Purchase #3	$37.81	5.828%	$40.0136	$40.01	$40.00	$40.00
Purchase #4	$64.56	12.628%	$72.7126	$72.71	$72.70	$72.70
Purchase #5	$208.98	13.455%	$237.0983	$237.10	$237.10	$237.10
Purchase #6	$159.30	11.667%	$177.8855	$177.89	$177.90	$177.90
Purchase #7	$233.83	4.672%	$244.7545	$244.75	$244.75	$244.80
7 purchase totals =	$986.31		$1,077.2742	$1,077.27	$1,077.25	$1,077.30