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	$233.45	9.802%	$256.3328	$256.33	$256.35	$256.30
Purchase #2	$9.47	9.472%	$10.367	$10.37	$10.35	$10.40
Purchase #3	$100.76	10.380%	$111.2189	$111.22	$111.20	$111.20
Purchase #4	$128.52	10.872%	$142.4927	$142.49	$142.50	$142.50
Purchase #5	$29.56	3.665%	$30.6434	$30.64	$30.65	$30.60
Purchase #6	$86.62	9.167%	$94.5605	$94.56	$94.55	$94.60
Purchase #7	$129.29	12.813%	$145.8559	$145.86	$145.85	$145.90
7 purchase totals =	$717.67		$791.4712	$791.47	$791.45	$791.50