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	$89.58	5.430%	$94.4442	$94.44	$94.45	$94.40
Purchase #2	$39.45	10.383%	$43.5461	$43.55	$43.55	$43.50
Purchase #3	$129.29	10.729%	$143.1615	$143.16	$143.15	$143.20
Purchase #4	$40.61	10.633%	$44.9281	$44.93	$44.95	$44.90
Purchase #5	$65.59	10.427%	$72.4291	$72.43	$72.45	$72.40
Purchase #6	$7.81	13.136%	$8.8359	$8.84	$8.85	$8.80
Purchase #7	$94.73	9.588%	$103.8127	$103.81	$103.80	$103.80
7 purchase totals =	$467.06		$511.1576	$511.16	$511.20	$511.00