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	$103.91	9.611%	$113.8968	$113.90	$113.90	$113.90
Purchase #2	$95.45	10.708%	$105.6708	$105.67	$105.65	$105.70
Purchase #3	$186.54	7.530%	$200.5865	$200.59	$200.60	$200.60
Purchase #4	$138.80	12.479%	$156.1209	$156.12	$156.10	$156.10
Purchase #5	$113.84	10.585%	$125.89	$125.89	$125.90	$125.90
Purchase #6	$161.35	12.585%	$181.6559	$181.66	$181.65	$181.70
Purchase #7	$19.43	11.748%	$21.7126	$21.71	$21.70	$21.70
7 purchase totals =	$819.32		$905.5335	$905.54	$905.50	$905.60