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	$111.30	3.254%	$114.9217	$114.92	$114.90	$114.90
Purchase #2	$29.52	7.407%	$31.7065	$31.71	$31.70	$31.70
Purchase #3	$71.32	3.192%	$73.5965	$73.60	$73.60	$73.60
Purchase #4	$44.60	8.465%	$48.3754	$48.38	$48.40	$48.40
Purchase #5	$217.54	10.582%	$240.5601	$240.56	$240.55	$240.60
Purchase #6	$150.89	12.347%	$169.5204	$169.52	$169.50	$169.50
Purchase #7	$13.40	6.737%	$14.3028	$14.30	$14.30	$14.30
7 purchase totals =	$638.57		$692.9834	$692.99	$692.95	$693.00