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	$189.64	13.652%	$215.5297	$215.53	$215.55	$215.50
Purchase #2	$86.53	4.543%	$90.4611	$90.46	$90.45	$90.50
Purchase #3	$210.34	8.522%	$228.2652	$228.27	$228.25	$228.30
Purchase #4	$56.49	4.866%	$59.2388	$59.24	$59.25	$59.20
Purchase #5	$126.52	12.391%	$142.1971	$142.20	$142.20	$142.20
Purchase #6	$119.46	12.568%	$134.4737	$134.47	$134.45	$134.50
Purchase #7	$12.51	10.738%	$13.8533	$13.85	$13.85	$13.90
7 purchase totals =	$801.49		$884.0189	$884.02	$884.00	$884.10