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	$174.82	5.315%	$184.1117	$184.11	$184.10	$184.10
Purchase #2	$44.81	9.843%	$49.2206	$49.22	$49.20	$49.20
Purchase #3	$131.43	9.478%	$143.8869	$143.89	$143.90	$143.90
Purchase #4	$45.75	7.441%	$49.1543	$49.15	$49.15	$49.20
Purchase #5	$108.66	13.626%	$123.466	$123.47	$123.45	$123.50
Purchase #6	$151.93	12.273%	$170.5764	$170.58	$170.60	$170.60
Purchase #7	$35.40	11.827%	$39.5868	$39.59	$39.60	$39.60
7 purchase totals =	$692.80		$760.0027	$760.01	$760.00	$760.10