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	$114.76	13.708%	$130.4913	$130.49	$130.50	$130.50
Purchase #2	$121.32	12.729%	$136.7628	$136.76	$136.75	$136.80
Purchase #3	$68.58	4.817%	$71.8835	$71.88	$71.90	$71.90
Purchase #4	$148.78	13.268%	$168.5201	$168.52	$168.50	$168.50
Purchase #5	$108.67	13.497%	$123.3372	$123.34	$123.35	$123.30
Purchase #6	$63.60	7.157%	$68.1519	$68.15	$68.15	$68.20
Purchase #7	$207.33	3.734%	$215.0717	$215.07	$215.05	$215.10
7 purchase totals =	$833.04		$914.2185	$914.21	$914.20	$914.30