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	$223.59	10.327%	$246.6801	$246.68	$246.70	$246.70
Purchase #2	$212.77	12.873%	$240.1599	$240.16	$240.15	$240.20
Purchase #3	$170.94	3.628%	$177.1417	$177.14	$177.15	$177.10
Purchase #4	$147.70	6.604%	$157.4541	$157.45	$157.45	$157.50
Purchase #5	$52.56	6.154%	$55.7945	$55.79	$55.80	$55.80
Purchase #6	$20.26	3.245%	$20.9174	$20.92	$20.90	$20.90
Purchase #7	$105.60	5.373%	$111.2739	$111.27	$111.25	$111.30
7 purchase totals =	$933.42		$1,009.4216	$1,009.41	$1,009.40	$1,009.50