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	$219.45	9.526%	$240.3548	$240.35	$240.35	$240.40
Purchase #2	$131.95	8.104%	$142.6432	$142.64	$142.65	$142.60
Purchase #3	$213.33	7.249%	$228.7943	$228.79	$228.80	$228.80
Purchase #4	$196.43	13.470%	$222.8891	$222.89	$222.90	$222.90
Purchase #5	$174.87	4.153%	$182.1324	$182.13	$182.15	$182.10
Purchase #6	$127.33	3.456%	$131.7305	$131.73	$131.75	$131.70
Purchase #7	$113.29	13.366%	$128.4323	$128.43	$128.45	$128.40
7 purchase totals =	$1,176.65		$1,276.9766	$1,276.96	$1,277.05	$1,276.90