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	$97.79	11.151%	$108.6946	$108.69	$108.70	$108.70
Purchase #2	$190.27	12.678%	$214.3924	$214.39	$214.40	$214.40
Purchase #3	$98.90	9.367%	$108.164	$108.16	$108.15	$108.20
Purchase #4	$84.69	5.729%	$89.5419	$89.54	$89.55	$89.50
Purchase #5	$174.85	5.456%	$184.3898	$184.39	$184.40	$184.40
Purchase #6	$44.45	7.731%	$47.8864	$47.89	$47.90	$47.90
Purchase #7	$224.69	13.829%	$255.7624	$255.76	$255.75	$255.80
7 purchase totals =	$915.64		$1,008.8315	$1,008.82	$1,008.85	$1,008.90