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	$100.30	11.208%	$111.5416	$111.54	$111.55	$111.50
Purchase #2	$29.56	13.241%	$33.474	$33.47	$33.45	$33.50
Purchase #3	$47.55	9.769%	$52.1952	$52.20	$52.20	$52.20
Purchase #4	$219.49	9.518%	$240.3811	$240.38	$240.40	$240.40
Purchase #5	$224.26	6.858%	$239.6398	$239.64	$239.65	$239.60
Purchase #6	$221.85	12.517%	$249.619	$249.62	$249.60	$249.60
Purchase #7	$85.43	4.244%	$89.0556	$89.06	$89.05	$89.10
7 purchase totals =	$928.44		$1,015.9063	$1,015.91	$1,015.90	$1,015.90