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	$86.81	9.320%	$94.9007	$94.90	$94.90	$94.90
Purchase #2	$134.79	7.849%	$145.3697	$145.37	$145.35	$145.40
Purchase #3	$78.86	5.759%	$83.4015	$83.40	$83.40	$83.40
Purchase #4	$39.82	8.450%	$43.1848	$43.18	$43.20	$43.20
Purchase #5	$148.83	11.575%	$166.0571	$166.06	$166.05	$166.10
Purchase #6	$140.84	12.549%	$158.514	$158.51	$158.50	$158.50
Purchase #7	$223.87	5.203%	$235.518	$235.52	$235.50	$235.50
7 purchase totals =	$853.82		$926.9458	$926.94	$926.90	$927.00