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	$47.36	9.795%	$51.9989	$52.00	$52.00	$52.00
Purchase #2	$205.82	6.342%	$218.8731	$218.87	$218.85	$218.90
Purchase #3	$235.40	10.596%	$260.343	$260.34	$260.35	$260.30
Purchase #4	$128.83	8.797%	$140.1632	$140.16	$140.15	$140.20
Purchase #5	$71.63	9.543%	$78.4657	$78.47	$78.45	$78.50
Purchase #6	$21.82	3.542%	$22.5929	$22.59	$22.60	$22.60
Purchase #7	$217.62	9.773%	$238.888	$238.89	$238.90	$238.90
7 purchase totals =	$928.48		$1,011.3248	$1,011.32	$1,011.30	$1,011.40