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	$242.95	9.382%	$265.7436	$265.74	$265.75	$265.70
Purchase #2	$100.77	4.861%	$105.6684	$105.67	$105.65	$105.70
Purchase #3	$93.98	3.745%	$97.4996	$97.50	$97.50	$97.50
Purchase #4	$197.25	12.476%	$221.8589	$221.86	$221.85	$221.90
Purchase #5	$127.28	6.345%	$135.3559	$135.36	$135.35	$135.40
Purchase #6	$163.48	6.396%	$173.9362	$173.94	$173.95	$173.90
Purchase #7	$101.78	9.404%	$111.3514	$111.35	$111.35	$111.40
7 purchase totals =	$1,027.49		$1,111.4140	$1,111.42	$1,111.40	$1,111.50