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	$219.90	5.320%	$231.5987	$231.60	$231.60	$231.60
Purchase #2	$33.27	6.867%	$35.5547	$35.55	$35.55	$35.60
Purchase #3	$114.45	10.171%	$126.0907	$126.09	$126.10	$126.10
Purchase #4	$52.84	3.338%	$54.6038	$54.60	$54.60	$54.60
Purchase #5	$169.72	7.182%	$181.9093	$181.91	$181.90	$181.90
Purchase #6	$59.87	12.559%	$67.3891	$67.39	$67.40	$67.40
Purchase #7	$207.87	7.702%	$223.8801	$223.88	$223.90	$223.90
7 purchase totals =	$857.92		$921.0264	$921.02	$921.05	$921.10