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	$5.60	4.404%	$5.8466	$5.85	$5.85	$5.80
Purchase #2	$48.38	7.510%	$52.0133	$52.01	$52.00	$52.00
Purchase #3	$173.85	6.108%	$184.4688	$184.47	$184.45	$184.50
Purchase #4	$84.98	6.702%	$90.6754	$90.68	$90.70	$90.70
Purchase #5	$96.47	13.705%	$109.6912	$109.69	$109.70	$109.70
Purchase #6	$19.80	9.612%	$21.7032	$21.70	$21.70	$21.70
Purchase #7	$6.78	7.159%	$7.2654	$7.27	$7.25	$7.30
7 purchase totals =	$435.86		$471.6639	$471.67	$471.65	$471.70