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	$78.28	13.278%	$88.674	$88.67	$88.65	$88.70
Purchase #2	$97.98	13.314%	$111.0251	$111.03	$111.05	$111.00
Purchase #3	$180.65	8.498%	$196.0016	$196.00	$196.00	$196.00
Purchase #4	$233.72	11.425%	$260.4225	$260.42	$260.40	$260.40
Purchase #5	$244.44	3.338%	$252.5994	$252.60	$252.60	$252.60
Purchase #6	$124.89	12.686%	$140.7335	$140.73	$140.75	$140.70
Purchase #7	$72.71	11.164%	$80.8273	$80.83	$80.85	$80.80
7 purchase totals =	$1,032.67		$1,130.2834	$1,130.28	$1,130.30	$1,130.20