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	$44.90	7.849%	$48.4242	$48.42	$48.40	$48.40
Purchase #2	$197.99	6.533%	$210.9247	$210.92	$210.90	$210.90
Purchase #3	$180.34	11.206%	$200.5489	$200.55	$200.55	$200.50
Purchase #4	$147.88	13.773%	$168.2475	$168.25	$168.25	$168.20
Purchase #5	$59.79	4.550%	$62.5104	$62.51	$62.50	$62.50
Purchase #6	$198.42	13.656%	$225.5162	$225.52	$225.50	$225.50
Purchase #7	$41.26	9.187%	$45.0506	$45.05	$45.05	$45.10
7 purchase totals =	$870.58		$961.2225	$961.22	$961.15	$961.10