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	$64.67	11.721%	$72.25	$72.25	$72.25	$72.30
Purchase #2	$21.62	13.725%	$24.5873	$24.59	$24.60	$24.60
Purchase #3	$124.39	13.112%	$140.7	$140.70	$140.70	$140.70
Purchase #4	$145.69	6.648%	$155.3755	$155.38	$155.40	$155.40
Purchase #5	$71.90	8.611%	$78.0913	$78.09	$78.10	$78.10
Purchase #6	$231.31	3.530%	$239.4752	$239.48	$239.50	$239.50
Purchase #7	$36.86	6.636%	$39.306	$39.31	$39.30	$39.30
7 purchase totals =	$696.44		$749.7853	$749.80	$749.85	$749.90