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	$156.43	10.851%	$173.4042	$173.40	$173.40	$173.40
Purchase #2	$110.96	3.338%	$114.6638	$114.66	$114.65	$114.70
Purchase #3	$119.82	11.711%	$133.8521	$133.85	$133.85	$133.90
Purchase #4	$89.75	13.793%	$102.1292	$102.13	$102.15	$102.10
Purchase #5	$71.55	9.368%	$78.2528	$78.25	$78.25	$78.30
Purchase #6	$222.57	6.546%	$237.1394	$237.14	$237.15	$237.10
Purchase #7	$81.35	6.730%	$86.8249	$86.82	$86.80	$86.80
7 purchase totals =	$852.43		$926.2664	$926.25	$926.25	$926.30