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	$177.96	13.803%	$202.5238	$202.52	$202.50	$202.50
Purchase #2	$206.59	4.503%	$215.8927	$215.89	$215.90	$215.90
Purchase #3	$111.77	11.219%	$124.3095	$124.31	$124.30	$124.30
Purchase #4	$120.64	13.622%	$137.0736	$137.07	$137.05	$137.10
Purchase #5	$33.79	6.261%	$35.9056	$35.91	$35.90	$35.90
Purchase #6	$36.62	3.366%	$37.8526	$37.85	$37.85	$37.90
Purchase #7	$103.99	5.175%	$109.3715	$109.37	$109.35	$109.40
7 purchase totals =	$791.36		$862.9293	$862.92	$862.85	$863.00