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	$134.88	6.765%	$144.0046	$144.00	$144.00	$144.00
Purchase #2	$219.87	12.536%	$247.4329	$247.43	$247.45	$247.40
Purchase #3	$119.33	6.430%	$127.0029	$127.00	$127.00	$127.00
Purchase #4	$89.32	12.531%	$100.5127	$100.51	$100.50	$100.50
Purchase #5	$58.56	12.106%	$65.6493	$65.65	$65.65	$65.60
Purchase #6	$18.65	4.819%	$19.5487	$19.55	$19.55	$19.50
Purchase #7	$228.80	3.807%	$237.5104	$237.51	$237.50	$237.50
7 purchase totals =	$869.41		$941.6615	$941.65	$941.65	$941.50