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	$72.35	4.766%	$75.7982	$75.80	$75.80	$75.80
Purchase #2	$7.92	7.109%	$8.483	$8.48	$8.50	$8.50
Purchase #3	$83.91	10.466%	$92.692	$92.69	$92.70	$92.70
Purchase #4	$54.34	9.803%	$59.667	$59.67	$59.65	$59.70
Purchase #5	$214.42	4.518%	$224.1075	$224.11	$224.10	$224.10
Purchase #6	$75.42	9.716%	$82.7478	$82.75	$82.75	$82.70
Purchase #7	$118.78	7.211%	$127.3452	$127.35	$127.35	$127.30
7 purchase totals =	$627.14		$670.8407	$670.85	$670.85	$670.80