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	$150.59	4.209%	$156.9283	$156.93	$156.95	$156.90
Purchase #2	$80.80	11.631%	$90.1978	$90.20	$90.20	$90.20
Purchase #3	$155.82	11.475%	$173.7003	$173.70	$173.70	$173.70
Purchase #4	$78.76	4.480%	$82.2884	$82.29	$82.30	$82.30
Purchase #5	$76.50	7.414%	$82.1717	$82.17	$82.15	$82.20
Purchase #6	$95.73	12.604%	$107.7958	$107.80	$107.80	$107.80
Purchase #7	$239.31	7.140%	$256.3967	$256.40	$256.40	$256.40
7 purchase totals =	$877.51		$949.4790	$949.49	$949.50	$949.50