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	$41.93	5.260%	$44.1355	$44.14	$44.15	$44.10
Purchase #2	$76.78	7.360%	$82.431	$82.43	$82.45	$82.40
Purchase #3	$243.97	6.679%	$260.2648	$260.26	$260.25	$260.30
Purchase #4	$48.98	11.107%	$54.4202	$54.42	$54.40	$54.40
Purchase #5	$104.53	4.451%	$109.1826	$109.18	$109.20	$109.20
Purchase #6	$65.51	11.575%	$73.0928	$73.09	$73.10	$73.10
Purchase #7	$134.38	5.683%	$142.0168	$142.02	$142.00	$142.00
7 purchase totals =	$716.08		$765.5437	$765.54	$765.55	$765.50