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	$109.26	4.359%	$114.0226	$114.02	$114.00	$114.00
Purchase #2	$157.38	13.748%	$179.0166	$179.02	$179.00	$179.00
Purchase #3	$38.92	10.287%	$42.9237	$42.92	$42.90	$42.90
Purchase #4	$103.56	4.243%	$107.9541	$107.95	$107.95	$108.00
Purchase #5	$132.47	10.473%	$146.3436	$146.34	$146.35	$146.30
Purchase #6	$186.71	12.426%	$209.9106	$209.91	$209.90	$209.90
Purchase #7	$35.72	12.680%	$40.2493	$40.25	$40.25	$40.20
7 purchase totals =	$764.02		$840.4205	$840.41	$840.35	$840.30