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	$69.31	3.240%	$71.5556	$71.56	$71.55	$71.60
Purchase #2	$56.36	6.415%	$59.9755	$59.98	$60.00	$60.00
Purchase #3	$161.75	4.138%	$168.4432	$168.44	$168.45	$168.40
Purchase #4	$102.28	3.444%	$105.8025	$105.80	$105.80	$105.80
Purchase #5	$136.88	12.768%	$154.3568	$154.36	$154.35	$154.40
Purchase #6	$123.38	13.397%	$139.9092	$139.91	$139.90	$139.90
Purchase #7	$240.97	10.725%	$266.814	$266.81	$266.80	$266.80
7 purchase totals =	$890.93		$966.8568	$966.86	$966.85	$966.90