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	$159.38	13.664%	$181.1577	$181.16	$181.15	$181.20
Purchase #2	$83.56	7.763%	$90.0468	$90.05	$90.05	$90.00
Purchase #3	$212.60	8.297%	$230.2394	$230.24	$230.25	$230.20
Purchase #4	$168.60	11.777%	$188.456	$188.46	$188.45	$188.50
Purchase #5	$95.47	5.207%	$100.4411	$100.44	$100.45	$100.40
Purchase #6	$90.62	9.620%	$99.3376	$99.34	$99.35	$99.30
Purchase #7	$157.62	7.166%	$168.915	$168.92	$168.90	$168.90
7 purchase totals =	$967.85		$1,058.5936	$1,058.61	$1,058.60	$1,058.50