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	$194.30	8.766%	$211.3323	$211.33	$211.35	$211.30
Purchase #2	$82.52	10.851%	$91.4742	$91.47	$91.45	$91.50
Purchase #3	$86.85	12.403%	$97.622	$97.62	$97.60	$97.60
Purchase #4	$156.50	11.510%	$174.5132	$174.51	$174.50	$174.50
Purchase #5	$223.70	12.430%	$251.5059	$251.51	$251.50	$251.50
Purchase #6	$64.94	5.447%	$68.4773	$68.48	$68.50	$68.50
Purchase #7	$129.33	11.386%	$144.0555	$144.06	$144.05	$144.10
7 purchase totals =	$938.14		$1,038.9804	$1,038.98	$1,038.95	$1,039.00