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	$55.94	6.202%	$59.4094	$59.41	$59.40	$59.40
Purchase #2	$153.75	7.633%	$165.4857	$165.49	$165.50	$165.50
Purchase #3	$161.39	4.364%	$168.4331	$168.43	$168.45	$168.40
Purchase #4	$182.67	7.303%	$196.0104	$196.01	$196.00	$196.00
Purchase #5	$143.61	11.850%	$160.6278	$160.63	$160.65	$160.60
Purchase #6	$177.94	6.496%	$189.499	$189.50	$189.50	$189.50
Purchase #7	$226.50	8.335%	$245.3788	$245.38	$245.40	$245.40
7 purchase totals =	$1,101.80		$1,184.8442	$1,184.85	$1,184.90	$1,184.80