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	$49.30	8.550%	$53.5152	$53.52	$53.50	$53.50
Purchase #2	$196.27	13.124%	$222.0285	$222.03	$222.05	$222.00
Purchase #3	$82.61	4.393%	$86.2391	$86.24	$86.25	$86.20
Purchase #4	$213.36	8.239%	$230.9387	$230.94	$230.95	$230.90
Purchase #5	$26.89	6.156%	$28.5453	$28.55	$28.55	$28.50
Purchase #6	$106.71	11.272%	$118.7384	$118.74	$118.75	$118.70
Purchase #7	$98.41	5.597%	$103.918	$103.92	$103.90	$103.90
7 purchase totals =	$773.55		$843.9232	$843.94	$843.95	$843.70