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	$25.75	9.400%	$28.1705	$28.17	$28.15	$28.20
Purchase #2	$28.81	10.666%	$31.8829	$31.88	$31.90	$31.90
Purchase #3	$200.66	7.390%	$215.4888	$215.49	$215.50	$215.50
Purchase #4	$225.73	13.224%	$255.5805	$255.58	$255.60	$255.60
Purchase #5	$93.35	5.756%	$98.7232	$98.72	$98.70	$98.70
Purchase #6	$222.85	7.414%	$239.3721	$239.37	$239.35	$239.40
Purchase #7	$141.59	9.352%	$154.8315	$154.83	$154.85	$154.80
7 purchase totals =	$938.74		$1,024.0495	$1,024.04	$1,024.05	$1,024.10