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	$72.28	9.264%	$78.976	$78.98	$79.00	$79.00
Purchase #2	$19.78	3.728%	$20.5174	$20.52	$20.50	$20.50
Purchase #3	$19.89	11.123%	$22.1024	$22.10	$22.10	$22.10
Purchase #4	$25.98	10.133%	$28.6126	$28.61	$28.60	$28.60
Purchase #5	$177.99	10.553%	$196.7733	$196.77	$196.75	$196.80
Purchase #6	$212.90	4.430%	$222.3315	$222.33	$222.35	$222.30
Purchase #7	$125.66	11.257%	$139.8055	$139.81	$139.80	$139.80
7 purchase totals =	$654.48		$709.1187	$709.12	$709.10	$709.10