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	$5.64	3.152%	$5.8178	$5.82	$5.80	$5.80
Purchase #2	$116.67	10.449%	$128.8608	$128.86	$128.85	$128.90
Purchase #3	$76.47	5.665%	$80.802	$80.80	$80.80	$80.80
Purchase #4	$33.32	6.563%	$35.5068	$35.51	$35.50	$35.50
Purchase #5	$96.33	6.721%	$102.8043	$102.80	$102.80	$102.80
Purchase #6	$207.67	11.349%	$231.2385	$231.24	$231.25	$231.20
Purchase #7	$166.82	4.225%	$173.8681	$173.87	$173.85	$173.90
7 purchase totals =	$702.92		$758.8983	$758.90	$758.85	$758.90