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	$138.47	8.564%	$150.3286	$150.33	$150.35	$150.30
Purchase #2	$131.95	5.808%	$139.6137	$139.61	$139.60	$139.60
Purchase #3	$30.59	13.619%	$34.7561	$34.76	$34.75	$34.80
Purchase #4	$123.30	3.545%	$127.671	$127.67	$127.65	$127.70
Purchase #5	$56.40	11.388%	$62.8228	$62.82	$62.80	$62.80
Purchase #6	$55.36	11.464%	$61.7065	$61.71	$61.70	$61.70
Purchase #7	$114.76	8.540%	$124.5605	$124.56	$124.55	$124.60
7 purchase totals =	$650.83		$701.4592	$701.46	$701.40	$701.50