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	$142.69	4.296%	$148.82	$148.82	$148.80	$148.80
Purchase #2	$101.30	10.572%	$112.0094	$112.01	$112.00	$112.00
Purchase #3	$176.79	10.800%	$195.8833	$195.88	$195.90	$195.90
Purchase #4	$248.61	4.442%	$259.6533	$259.65	$259.65	$259.70
Purchase #5	$161.76	6.427%	$172.1563	$172.16	$172.15	$172.20
Purchase #6	$17.81	4.538%	$18.6182	$18.62	$18.60	$18.60
Purchase #7	$150.74	9.493%	$165.0497	$165.05	$165.05	$165.00
7 purchase totals =	$999.70		$1,072.1902	$1,072.19	$1,072.15	$1,072.20