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	$50.92	3.790%	$52.8499	$52.85	$52.85	$52.80
Purchase #2	$82.96	6.439%	$88.3018	$88.30	$88.30	$88.30
Purchase #3	$165.77	9.612%	$181.7038	$181.70	$181.70	$181.70
Purchase #4	$203.28	12.357%	$228.3993	$228.40	$228.40	$228.40
Purchase #5	$97.76	3.254%	$100.9411	$100.94	$100.95	$100.90
Purchase #6	$215.92	5.853%	$228.5578	$228.56	$228.55	$228.60
Purchase #7	$235.29	8.592%	$255.5061	$255.51	$255.50	$255.50
7 purchase totals =	$1,051.90		$1,136.2598	$1,136.26	$1,136.25	$1,136.20