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	$173.99	12.792%	$196.2468	$196.25	$196.25	$196.20
Purchase #2	$170.83	6.340%	$181.6606	$181.66	$181.65	$181.70
Purchase #3	$46.25	12.328%	$51.9517	$51.95	$51.95	$52.00
Purchase #4	$104.52	6.444%	$111.2553	$111.26	$111.25	$111.30
Purchase #5	$111.95	13.293%	$126.8315	$126.83	$126.85	$126.80
Purchase #6	$7.38	7.419%	$7.9275	$7.93	$7.95	$7.90
Purchase #7	$170.72	8.380%	$185.0263	$185.03	$185.05	$185.00
7 purchase totals =	$785.64		$860.8997	$860.91	$860.95	$860.90