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	$69.25	3.259%	$71.5069	$71.51	$71.50	$71.50
Purchase #2	$199.54	8.190%	$215.8823	$215.88	$215.90	$215.90
Purchase #3	$77.97	9.645%	$85.4902	$85.49	$85.50	$85.50
Purchase #4	$161.32	7.737%	$173.8013	$173.80	$173.80	$173.80
Purchase #5	$100.55	3.318%	$103.8862	$103.89	$103.90	$103.90
Purchase #6	$146.61	8.182%	$158.6056	$158.61	$158.60	$158.60
Purchase #7	$168.88	5.344%	$177.9049	$177.90	$177.90	$177.90
7 purchase totals =	$924.12		$987.0774	$987.08	$987.10	$987.10