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	$118.38	10.657%	$130.9958	$131.00	$131.00	$131.00
Purchase #2	$6.75	10.508%	$7.4593	$7.46	$7.45	$7.50
Purchase #3	$159.49	4.492%	$166.6543	$166.65	$166.65	$166.70
Purchase #4	$77.76	6.440%	$82.7677	$82.77	$82.75	$82.80
Purchase #5	$91.29	12.106%	$102.3416	$102.34	$102.35	$102.30
Purchase #6	$34.46	3.277%	$35.5893	$35.59	$35.60	$35.60
Purchase #7	$169.56	13.528%	$192.4981	$192.50	$192.50	$192.50
7 purchase totals =	$657.69		$718.3061	$718.31	$718.30	$718.40