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	$78.86	13.745%	$89.6993	$89.70	$89.70	$89.70
Purchase #2	$6.77	4.311%	$7.0619	$7.06	$7.05	$7.10
Purchase #3	$71.72	10.113%	$78.973	$78.97	$78.95	$79.00
Purchase #4	$184.82	7.536%	$198.748	$198.75	$198.75	$198.70
Purchase #5	$145.64	3.304%	$150.4519	$150.45	$150.45	$150.50
Purchase #6	$150.58	12.709%	$169.7172	$169.72	$169.70	$169.70
Purchase #7	$21.64	12.395%	$24.3223	$24.32	$24.30	$24.30
7 purchase totals =	$660.03		$718.9736	$718.97	$718.90	$719.00