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	$67.81	7.811%	$73.1066	$73.11	$73.10	$73.10
Purchase #2	$50.80	5.556%	$53.6224	$53.62	$53.60	$53.60
Purchase #3	$66.48	8.577%	$72.182	$72.18	$72.20	$72.20
Purchase #4	$143.36	8.393%	$155.3922	$155.39	$155.40	$155.40
Purchase #5	$122.50	8.837%	$133.3253	$133.33	$133.35	$133.30
Purchase #6	$95.31	10.142%	$104.9763	$104.98	$105.00	$105.00
Purchase #7	$13.56	6.797%	$14.4817	$14.48	$14.50	$14.50
7 purchase totals =	$559.82		$607.0865	$607.09	$607.15	$607.10