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	$200.57	11.795%	$224.2272	$224.23	$224.25	$224.20
Purchase #2	$76.82	7.330%	$82.4509	$82.45	$82.45	$82.50
Purchase #3	$156.81	5.691%	$165.7341	$165.73	$165.75	$165.70
Purchase #4	$86.71	5.798%	$91.7374	$91.74	$91.75	$91.70
Purchase #5	$188.45	10.124%	$207.5287	$207.53	$207.55	$207.50
Purchase #6	$229.60	11.311%	$255.5701	$255.57	$255.55	$255.60
Purchase #7	$213.73	7.139%	$228.9882	$228.99	$229.00	$229.00
7 purchase totals =	$1,152.69		$1,256.2366	$1,256.24	$1,256.30	$1,256.20