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	$137.86	3.410%	$142.561	$142.56	$142.55	$142.60
Purchase #2	$115.31	10.516%	$127.436	$127.44	$127.45	$127.40
Purchase #3	$214.96	9.766%	$235.953	$235.95	$235.95	$236.00
Purchase #4	$112.48	10.863%	$124.6987	$124.70	$124.70	$124.70
Purchase #5	$209.74	12.421%	$235.7918	$235.79	$235.80	$235.80
Purchase #6	$112.65	4.727%	$117.975	$117.98	$118.00	$118.00
Purchase #7	$103.89	12.141%	$116.5033	$116.50	$116.50	$116.50
7 purchase totals =	$1,006.89		$1,100.9188	$1,100.92	$1,100.95	$1,101.00