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	$41.52	10.659%	$45.9456	$45.95	$45.95	$45.90
Purchase #2	$67.95	10.262%	$74.923	$74.92	$74.90	$74.90
Purchase #3	$82.45	3.242%	$85.123	$85.12	$85.10	$85.10
Purchase #4	$171.43	6.102%	$181.8907	$181.89	$181.90	$181.90
Purchase #5	$228.90	9.453%	$250.5379	$250.54	$250.55	$250.50
Purchase #6	$47.55	13.216%	$53.8342	$53.83	$53.85	$53.80
Purchase #7	$110.96	6.194%	$117.8329	$117.83	$117.85	$117.80
7 purchase totals =	$750.76		$810.0873	$810.08	$810.10	$809.90