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	$99.49	12.225%	$111.6527	$111.65	$111.65	$111.70
Purchase #2	$71.57	12.511%	$80.5241	$80.52	$80.50	$80.50
Purchase #3	$99.43	12.107%	$111.468	$111.47	$111.45	$111.50
Purchase #4	$167.42	10.363%	$184.7697	$184.77	$184.75	$184.80
Purchase #5	$11.43	3.389%	$11.8174	$11.82	$11.80	$11.80
Purchase #6	$77.97	5.458%	$82.2256	$82.23	$82.25	$82.20
Purchase #7	$63.99	12.322%	$71.8748	$71.87	$71.85	$71.90
7 purchase totals =	$591.30		$654.3323	$654.33	$654.25	$654.40