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	$107.81	3.162%	$111.219	$111.22	$111.20	$111.20
Purchase #2	$73.51	10.675%	$81.3572	$81.36	$81.35	$81.40
Purchase #3	$159.90	7.254%	$171.4991	$171.50	$171.50	$171.50
Purchase #4	$176.71	4.709%	$185.0313	$185.03	$185.05	$185.00
Purchase #5	$236.67	5.204%	$248.9863	$248.99	$249.00	$249.00
Purchase #6	$178.82	6.364%	$190.2001	$190.20	$190.20	$190.20
Purchase #7	$89.35	8.757%	$97.1744	$97.17	$97.15	$97.20
7 purchase totals =	$1,022.77		$1,085.4674	$1,085.47	$1,085.45	$1,085.50