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	$17.95	11.124%	$19.9468	$19.95	$19.95	$19.90
Purchase #2	$67.95	7.224%	$72.8587	$72.86	$72.85	$72.90
Purchase #3	$105.96	5.114%	$111.3788	$111.38	$111.40	$111.40
Purchase #4	$75.34	9.265%	$82.3203	$82.32	$82.30	$82.30
Purchase #5	$46.98	4.796%	$49.2332	$49.23	$49.25	$49.20
Purchase #6	$121.68	12.676%	$137.1042	$137.10	$137.10	$137.10
Purchase #7	$157.96	12.849%	$178.2563	$178.26	$178.25	$178.30
7 purchase totals =	$593.82		$651.0983	$651.10	$651.10	$651.10