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	$100.89	9.178%	$110.1497	$110.15	$110.15	$110.10
Purchase #2	$246.97	3.279%	$255.0681	$255.07	$255.05	$255.10
Purchase #3	$86.98	10.232%	$95.8798	$95.88	$95.90	$95.90
Purchase #4	$51.50	11.479%	$57.4117	$57.41	$57.40	$57.40
Purchase #5	$235.72	8.415%	$255.5558	$255.56	$255.55	$255.60
Purchase #6	$35.26	13.724%	$40.0991	$40.10	$40.10	$40.10
Purchase #7	$100.29	5.154%	$105.4589	$105.46	$105.45	$105.50
7 purchase totals =	$857.61		$919.6231	$919.63	$919.60	$919.70