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	$76.56	3.874%	$79.5259	$79.53	$79.55	$79.50
Purchase #2	$162.89	6.119%	$172.8572	$172.86	$172.85	$172.90
Purchase #3	$14.35	10.158%	$15.8077	$15.81	$15.80	$15.80
Purchase #4	$88.57	7.572%	$95.2765	$95.28	$95.30	$95.30
Purchase #5	$138.38	11.788%	$154.6922	$154.69	$154.70	$154.70
Purchase #6	$211.68	4.160%	$220.4859	$220.49	$220.50	$220.50
Purchase #7	$201.38	10.506%	$222.537	$222.54	$222.55	$222.50
7 purchase totals =	$893.81		$961.1824	$961.20	$961.25	$961.20