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	$107.30	3.540%	$111.0984	$111.10	$111.10	$111.10
Purchase #2	$89.84	11.203%	$99.9048	$99.90	$99.90	$99.90
Purchase #3	$226.59	3.190%	$233.8182	$233.82	$233.80	$233.80
Purchase #4	$165.83	4.185%	$172.77	$172.77	$172.75	$172.80
Purchase #5	$148.93	4.482%	$155.605	$155.61	$155.60	$155.60
Purchase #6	$130.41	4.289%	$136.0033	$136.00	$136.00	$136.00
Purchase #7	$114.99	9.714%	$126.1601	$126.16	$126.15	$126.20
7 purchase totals =	$983.89		$1,035.3598	$1,035.36	$1,035.30	$1,035.40