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	$114.99	9.689%	$126.1314	$126.13	$126.15	$126.10
Purchase #2	$150.69	6.221%	$160.0644	$160.06	$160.05	$160.10
Purchase #3	$228.73	10.730%	$253.2727	$253.27	$253.25	$253.30
Purchase #4	$163.68	3.113%	$168.7754	$168.78	$168.80	$168.80
Purchase #5	$10.43	9.300%	$11.4	$11.40	$11.40	$11.40
Purchase #6	$171.35	13.645%	$194.7307	$194.73	$194.75	$194.70
Purchase #7	$158.48	8.225%	$171.515	$171.52	$171.50	$171.50
7 purchase totals =	$998.35		$1,085.8896	$1,085.89	$1,085.90	$1,085.90