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	$41.45	9.596%	$45.4275	$45.43	$45.45	$45.40
Purchase #2	$112.38	3.670%	$116.5043	$116.50	$116.50	$116.50
Purchase #3	$197.69	7.269%	$212.0601	$212.06	$212.05	$212.10
Purchase #4	$52.80	12.464%	$59.381	$59.38	$59.40	$59.40
Purchase #5	$242.89	9.851%	$266.8171	$266.82	$266.80	$266.80
Purchase #6	$39.40	4.661%	$41.2364	$41.24	$41.25	$41.20
Purchase #7	$70.61	9.122%	$77.051	$77.05	$77.05	$77.10
7 purchase totals =	$757.22		$818.4774	$818.48	$818.50	$818.50