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	$75.51	10.630%	$83.5367	$83.54	$83.55	$83.50
Purchase #2	$47.77	6.805%	$51.0207	$51.02	$51.00	$51.00
Purchase #3	$31.79	5.599%	$33.5699	$33.57	$33.55	$33.60
Purchase #4	$14.54	5.403%	$15.3256	$15.33	$15.35	$15.30
Purchase #5	$69.50	4.740%	$72.7943	$72.79	$72.80	$72.80
Purchase #6	$213.77	11.610%	$238.5887	$238.59	$238.60	$238.60
Purchase #7	$16.65	9.625%	$18.2526	$18.25	$18.25	$18.30
7 purchase totals =	$469.53		$513.0885	$513.09	$513.10	$513.10