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	$74.70	10.764%	$82.7407	$82.74	$82.75	$82.70
Purchase #2	$100.33	8.171%	$108.528	$108.53	$108.55	$108.50
Purchase #3	$41.75	12.380%	$46.9187	$46.92	$46.90	$46.90
Purchase #4	$101.62	9.828%	$111.6072	$111.61	$111.60	$111.60
Purchase #5	$229.27	3.403%	$237.0721	$237.07	$237.05	$237.10
Purchase #6	$229.25	8.761%	$249.3346	$249.33	$249.35	$249.30
Purchase #7	$230.93	9.855%	$253.6882	$253.69	$253.70	$253.70
7 purchase totals =	$1,007.85		$1,089.8895	$1,089.89	$1,089.90	$1,089.80