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	$131.40	10.643%	$145.3849	$145.38	$145.40	$145.40
Purchase #2	$96.90	3.688%	$100.4737	$100.47	$100.45	$100.50
Purchase #3	$155.88	9.214%	$170.2428	$170.24	$170.25	$170.20
Purchase #4	$93.38	8.563%	$101.3761	$101.38	$101.40	$101.40
Purchase #5	$55.85	13.137%	$63.187	$63.19	$63.20	$63.20
Purchase #6	$247.62	8.518%	$268.7123	$268.71	$268.70	$268.70
Purchase #7	$238.35	7.198%	$255.5064	$255.51	$255.50	$255.50
7 purchase totals =	$1,019.38		$1,104.8832	$1,104.88	$1,104.90	$1,104.90